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	$135.33	7.113%	$144.956	$144.96	$144.95	$145.00
Purchase #2	$58.87	3.697%	$61.0464	$61.05	$61.05	$61.00
Purchase #3	$101.46	8.841%	$110.4301	$110.43	$110.45	$110.40
Purchase #4	$247.69	13.136%	$280.2266	$280.23	$280.25	$280.20
Purchase #5	$166.30	4.416%	$173.6438	$173.64	$173.65	$173.60
Purchase #6	$165.42	8.756%	$179.9042	$179.90	$179.90	$179.90
Purchase #7	$149.39	6.312%	$158.8195	$158.82	$158.80	$158.80
7 purchase totals =	$1,024.46		$1,109.0266	$1,109.03	$1,109.05	$1,108.90