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	$111.88	13.756%	$127.2702	$127.27	$127.25	$127.30
Purchase #2	$178.99	7.117%	$191.7287	$191.73	$191.75	$191.70
Purchase #3	$244.98	7.481%	$263.307	$263.31	$263.30	$263.30
Purchase #4	$202.37	4.775%	$212.0332	$212.03	$212.05	$212.00
Purchase #5	$72.52	13.478%	$82.2942	$82.29	$82.30	$82.30
Purchase #6	$59.65	6.451%	$63.498	$63.50	$63.50	$63.50
Purchase #7	$214.31	7.505%	$230.394	$230.39	$230.40	$230.40
7 purchase totals =	$1,084.70		$1,170.5253	$1,170.52	$1,170.55	$1,170.50