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	$42.60	11.817%	$47.634	$47.63	$47.65	$47.60
Purchase #2	$245.49	13.343%	$278.2457	$278.25	$278.25	$278.20
Purchase #3	$125.43	8.458%	$136.0389	$136.04	$136.05	$136.00
Purchase #4	$93.57	6.150%	$99.3246	$99.32	$99.30	$99.30
Purchase #5	$108.43	3.165%	$111.8618	$111.86	$111.85	$111.90
Purchase #6	$204.67	12.362%	$229.9713	$229.97	$229.95	$230.00
Purchase #7	$146.27	12.555%	$164.6342	$164.63	$164.65	$164.60
7 purchase totals =	$966.46		$1,067.7105	$1,067.70	$1,067.70	$1,067.60