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	$166.81	4.520%	$174.3498	$174.35	$174.35	$174.30
Purchase #2	$112.30	4.301%	$117.13	$117.13	$117.15	$117.10
Purchase #3	$224.62	7.256%	$240.9184	$240.92	$240.90	$240.90
Purchase #4	$40.51	12.332%	$45.5057	$45.51	$45.50	$45.50
Purchase #5	$215.92	6.300%	$229.523	$229.52	$229.50	$229.50
Purchase #6	$237.73	6.547%	$253.2942	$253.29	$253.30	$253.30
Purchase #7	$45.71	3.693%	$47.3981	$47.40	$47.40	$47.40
7 purchase totals =	$1,043.60		$1,108.1192	$1,108.12	$1,108.10	$1,108.00