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	$55.51	10.524%	$61.3519	$61.35	$61.35	$61.40
Purchase #2	$113.59	3.429%	$117.485	$117.49	$117.50	$117.50
Purchase #3	$210.54	5.514%	$222.1492	$222.15	$222.15	$222.10
Purchase #4	$94.98	8.586%	$103.135	$103.14	$103.15	$103.10
Purchase #5	$174.93	5.751%	$184.9902	$184.99	$185.00	$185.00
Purchase #6	$244.44	9.185%	$266.8918	$266.89	$266.90	$266.90
Purchase #7	$201.72	10.710%	$223.3242	$223.32	$223.30	$223.30
7 purchase totals =	$1,095.71		$1,179.3273	$1,179.33	$1,179.35	$1,179.30