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	$201.40	10.611%	$222.7706	$222.77	$222.75	$222.80
Purchase #2	$79.52	11.197%	$88.4239	$88.42	$88.40	$88.40
Purchase #3	$40.37	10.609%	$44.6529	$44.65	$44.65	$44.70
Purchase #4	$50.64	5.697%	$53.525	$53.53	$53.55	$53.50
Purchase #5	$176.38	6.525%	$187.8888	$187.89	$187.90	$187.90
Purchase #6	$170.51	6.388%	$181.4022	$181.40	$181.40	$181.40
Purchase #7	$200.74	11.518%	$223.8612	$223.86	$223.85	$223.90
7 purchase totals =	$919.56		$1,002.5246	$1,002.52	$1,002.50	$1,002.60