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	$174.74	11.169%	$194.2567	$194.26	$194.25	$194.30
Purchase #2	$177.67	4.561%	$185.7735	$185.77	$185.75	$185.80
Purchase #3	$113.75	13.360%	$128.947	$128.95	$128.95	$128.90
Purchase #4	$194.91	5.755%	$206.1271	$206.13	$206.15	$206.10
Purchase #5	$38.52	4.667%	$40.3177	$40.32	$40.30	$40.30
Purchase #6	$84.34	13.610%	$95.8187	$95.82	$95.80	$95.80
Purchase #7	$231.85	4.663%	$242.6612	$242.66	$242.65	$242.70
7 purchase totals =	$1,015.78		$1,093.9019	$1,093.91	$1,093.85	$1,093.90