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	$100.25	11.358%	$111.6364	$111.64	$111.65	$111.60
Purchase #2	$70.57	11.369%	$78.5931	$78.59	$78.60	$78.60
Purchase #3	$32.87	5.639%	$34.7235	$34.72	$34.70	$34.70
Purchase #4	$89.99	7.260%	$96.5233	$96.52	$96.50	$96.50
Purchase #5	$97.67	12.744%	$110.1171	$110.12	$110.10	$110.10
Purchase #6	$174.51	5.389%	$183.9143	$183.91	$183.90	$183.90
Purchase #7	$129.92	10.252%	$143.2394	$143.24	$143.25	$143.20
7 purchase totals =	$695.78		$758.7471	$758.74	$758.70	$758.60