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	$116.64	5.717%	$123.3083	$123.31	$123.30	$123.30
Purchase #2	$174.48	3.398%	$180.4088	$180.41	$180.40	$180.40
Purchase #3	$204.92	8.442%	$222.2193	$222.22	$222.20	$222.20
Purchase #4	$216.95	3.434%	$224.4001	$224.40	$224.40	$224.40
Purchase #5	$65.90	6.302%	$70.053	$70.05	$70.05	$70.10
Purchase #6	$173.69	10.363%	$191.6895	$191.69	$191.70	$191.70
Purchase #7	$152.88	7.859%	$164.8948	$164.89	$164.90	$164.90
7 purchase totals =	$1,105.46		$1,176.9738	$1,176.97	$1,176.95	$1,177.00