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	$106.58	11.696%	$119.0456	$119.05	$119.05	$119.00
Purchase #2	$129.30	10.301%	$142.6192	$142.62	$142.60	$142.60
Purchase #3	$243.67	11.542%	$271.7944	$271.79	$271.80	$271.80
Purchase #4	$196.79	7.549%	$211.6457	$211.65	$211.65	$211.60
Purchase #5	$194.72	12.191%	$218.4583	$218.46	$218.45	$218.50
Purchase #6	$29.37	12.819%	$33.1349	$33.13	$33.15	$33.10
Purchase #7	$89.88	7.794%	$96.8852	$96.89	$96.90	$96.90
7 purchase totals =	$990.31		$1,093.5833	$1,093.59	$1,093.60	$1,093.50