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	$233.99	7.444%	$251.4082	$251.41	$251.40	$251.40
Purchase #2	$51.52	10.371%	$56.8631	$56.86	$56.85	$56.90
Purchase #3	$148.88	4.290%	$155.267	$155.27	$155.25	$155.30
Purchase #4	$180.79	4.425%	$188.79	$188.79	$188.80	$188.80
Purchase #5	$49.49	9.489%	$54.1861	$54.19	$54.20	$54.20
Purchase #6	$127.78	13.810%	$145.4264	$145.43	$145.45	$145.40
Purchase #7	$157.89	6.223%	$167.7155	$167.72	$167.70	$167.70
7 purchase totals =	$950.34		$1,019.6563	$1,019.67	$1,019.65	$1,019.70