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	$158.79	3.473%	$164.3048	$164.30	$164.30	$164.30
Purchase #2	$85.71	4.532%	$89.5944	$89.59	$89.60	$89.60
Purchase #3	$57.50	12.608%	$64.7496	$64.75	$64.75	$64.70
Purchase #4	$74.90	13.817%	$85.2489	$85.25	$85.25	$85.20
Purchase #5	$159.40	4.389%	$166.3961	$166.40	$166.40	$166.40
Purchase #6	$95.49	6.388%	$101.5899	$101.59	$101.60	$101.60
Purchase #7	$168.42	8.303%	$182.4039	$182.40	$182.40	$182.40
7 purchase totals =	$800.21		$854.2876	$854.28	$854.30	$854.20