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	$227.72	11.839%	$254.6798	$254.68	$254.70	$254.70
Purchase #2	$238.65	12.676%	$268.9013	$268.90	$268.90	$268.90
Purchase #3	$97.77	6.416%	$104.0429	$104.04	$104.05	$104.00
Purchase #4	$36.64	11.631%	$40.9016	$40.90	$40.90	$40.90
Purchase #5	$45.97	10.257%	$50.6851	$50.69	$50.70	$50.70
Purchase #6	$225.88	10.813%	$250.3044	$250.30	$250.30	$250.30
Purchase #7	$104.28	6.557%	$111.1176	$111.12	$111.10	$111.10
7 purchase totals =	$976.91		$1,080.6327	$1,080.63	$1,080.65	$1,080.60