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	$76.51	7.456%	$82.2146	$82.21	$82.20	$82.20
Purchase #2	$202.82	3.800%	$210.5272	$210.53	$210.55	$210.50
Purchase #3	$149.37	12.568%	$168.1428	$168.14	$168.15	$168.10
Purchase #4	$233.67	7.311%	$250.7536	$250.75	$250.75	$250.80
Purchase #5	$235.49	6.709%	$251.289	$251.29	$251.30	$251.30
Purchase #6	$84.91	5.454%	$89.541	$89.54	$89.55	$89.50
Purchase #7	$198.40	5.296%	$208.9073	$208.91	$208.90	$208.90
7 purchase totals =	$1,181.17		$1,261.3755	$1,261.37	$1,261.40	$1,261.30