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	$90.75	7.167%	$97.2541	$97.25	$97.25	$97.30
Purchase #2	$18.39	13.848%	$20.9366	$20.94	$20.95	$20.90
Purchase #3	$89.86	7.760%	$96.8331	$96.83	$96.85	$96.80
Purchase #4	$86.34	4.369%	$90.1122	$90.11	$90.10	$90.10
Purchase #5	$147.88	7.408%	$158.835	$158.84	$158.85	$158.80
Purchase #6	$51.69	6.864%	$55.238	$55.24	$55.25	$55.20
Purchase #7	$60.85	7.455%	$65.3864	$65.39	$65.40	$65.40
7 purchase totals =	$545.76		$584.5954	$584.60	$584.65	$584.50