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	$223.81	13.536%	$254.1049	$254.10	$254.10	$254.10
Purchase #2	$200.76	10.166%	$221.1693	$221.17	$221.15	$221.20
Purchase #3	$86.78	4.309%	$90.5194	$90.52	$90.50	$90.50
Purchase #4	$126.33	12.737%	$142.4207	$142.42	$142.40	$142.40
Purchase #5	$93.91	4.874%	$98.4872	$98.49	$98.50	$98.50
Purchase #6	$132.99	12.518%	$149.6377	$149.64	$149.65	$149.60
Purchase #7	$156.38	6.479%	$166.5119	$166.51	$166.50	$166.50
7 purchase totals =	$1,020.96		$1,122.8511	$1,122.85	$1,122.80	$1,122.80