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	$233.86	5.801%	$247.4262	$247.43	$247.45	$247.40
Purchase #2	$211.53	4.421%	$220.8817	$220.88	$220.90	$220.90
Purchase #3	$168.29	3.656%	$174.4427	$174.44	$174.45	$174.40
Purchase #4	$129.34	10.335%	$142.7073	$142.71	$142.70	$142.70
Purchase #5	$91.69	8.467%	$99.4534	$99.45	$99.45	$99.50
Purchase #6	$67.30	5.751%	$71.1704	$71.17	$71.15	$71.20
Purchase #7	$183.44	7.350%	$196.9228	$196.92	$196.90	$196.90
7 purchase totals =	$1,085.45		$1,153.0045	$1,153.00	$1,153.00	$1,153.00