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	$73.75	4.238%	$76.8755	$76.88	$76.90	$76.90
Purchase #2	$135.72	7.522%	$145.9289	$145.93	$145.95	$145.90
Purchase #3	$165.72	5.689%	$175.1478	$175.15	$175.15	$175.10
Purchase #4	$167.62	5.250%	$176.4201	$176.42	$176.40	$176.40
Purchase #5	$204.54	6.826%	$218.5019	$218.50	$218.50	$218.50
Purchase #6	$65.74	8.842%	$71.5527	$71.55	$71.55	$71.60
Purchase #7	$29.98	8.275%	$32.4608	$32.46	$32.45	$32.50
7 purchase totals =	$843.07		$896.8877	$896.89	$896.90	$896.90