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	$223.44	12.647%	$251.6985	$251.70	$251.70	$251.70
Purchase #2	$49.74	7.568%	$53.5043	$53.50	$53.50	$53.50
Purchase #3	$169.86	3.780%	$176.2807	$176.28	$176.30	$176.30
Purchase #4	$162.70	7.821%	$175.4248	$175.42	$175.40	$175.40
Purchase #5	$42.98	6.479%	$45.7647	$45.76	$45.75	$45.80
Purchase #6	$155.87	9.729%	$171.0346	$171.03	$171.05	$171.00
Purchase #7	$223.80	6.413%	$238.1523	$238.15	$238.15	$238.20
7 purchase totals =	$1,028.39		$1,111.8599	$1,111.84	$1,111.85	$1,111.90