Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$105.33	7.317%	$113.037	$113.04	$113.05	$113.00
Purchase #2	$234.86	6.488%	$250.0977	$250.10	$250.10	$250.10
Purchase #3	$191.47	9.738%	$210.1153	$210.12	$210.10	$210.10
Purchase #4	$148.88	12.693%	$167.7773	$167.78	$167.80	$167.80
Purchase #5	$122.59	4.869%	$128.5589	$128.56	$128.55	$128.60
Purchase #6	$225.82	8.267%	$244.4885	$244.49	$244.50	$244.50
Purchase #7	$102.52	11.549%	$114.36	$114.36	$114.35	$114.40
7 purchase totals =	$1,131.47		$1,228.4347	$1,228.45	$1,228.45	$1,228.50