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	$51.84	7.576%	$55.7674	$55.77	$55.75	$55.80
Purchase #2	$228.72	7.261%	$245.3274	$245.33	$245.35	$245.30
Purchase #3	$66.50	7.560%	$71.5274	$71.53	$71.55	$71.50
Purchase #4	$118.61	7.606%	$127.6315	$127.63	$127.65	$127.60
Purchase #5	$126.59	9.111%	$138.1236	$138.12	$138.10	$138.10
Purchase #6	$30.77	4.522%	$32.1614	$32.16	$32.15	$32.20
Purchase #7	$159.76	7.585%	$171.8778	$171.88	$171.90	$171.90
7 purchase totals =	$782.79		$842.4165	$842.42	$842.45	$842.40