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	$91.78	10.658%	$101.5619	$101.56	$101.55	$101.60
Purchase #2	$77.91	5.445%	$82.1522	$82.15	$82.15	$82.20
Purchase #3	$29.83	5.312%	$31.4146	$31.41	$31.40	$31.40
Purchase #4	$58.89	9.501%	$64.4851	$64.49	$64.50	$64.50
Purchase #5	$71.58	9.287%	$78.2276	$78.23	$78.25	$78.20
Purchase #6	$108.51	3.150%	$111.9281	$111.93	$111.95	$111.90
Purchase #7	$43.59	5.637%	$46.0472	$46.05	$46.05	$46.00
7 purchase totals =	$482.09		$515.8167	$515.82	$515.85	$515.80