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	$179.66	9.561%	$196.8373	$196.84	$196.85	$196.80
Purchase #2	$91.91	5.470%	$96.9375	$96.94	$96.95	$96.90
Purchase #3	$31.69	7.611%	$34.1019	$34.10	$34.10	$34.10
Purchase #4	$21.86	4.157%	$22.7687	$22.77	$22.75	$22.80
Purchase #5	$138.51	3.641%	$143.5531	$143.55	$143.55	$143.60
Purchase #6	$10.76	3.283%	$11.1133	$11.11	$11.10	$11.10
Purchase #7	$39.71	12.276%	$44.5848	$44.58	$44.60	$44.60
7 purchase totals =	$514.10		$549.8966	$549.89	$549.90	$549.90