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	$19.92	4.482%	$20.8128	$20.81	$20.80	$20.80
Purchase #2	$202.95	13.216%	$229.7719	$229.77	$229.75	$229.80
Purchase #3	$217.64	12.713%	$245.3086	$245.31	$245.30	$245.30
Purchase #4	$149.78	10.681%	$165.778	$165.78	$165.80	$165.80
Purchase #5	$6.51	12.786%	$7.3424	$7.34	$7.35	$7.30
Purchase #6	$90.97	4.451%	$95.0191	$95.02	$95.00	$95.00
Purchase #7	$146.65	3.856%	$152.3048	$152.30	$152.30	$152.30
7 purchase totals =	$834.42		$916.3376	$916.33	$916.30	$916.30