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	$145.90	4.555%	$152.5457	$152.55	$152.55	$152.50
Purchase #2	$232.46	9.326%	$254.1392	$254.14	$254.15	$254.10
Purchase #3	$180.79	5.491%	$190.7172	$190.72	$190.70	$190.70
Purchase #4	$40.76	13.370%	$46.2096	$46.21	$46.20	$46.20
Purchase #5	$230.59	5.612%	$243.5307	$243.53	$243.55	$243.50
Purchase #6	$71.43	10.539%	$78.958	$78.96	$78.95	$79.00
Purchase #7	$60.52	4.463%	$63.221	$63.22	$63.20	$63.20
7 purchase totals =	$962.45		$1,029.3214	$1,029.33	$1,029.30	$1,029.20