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	$211.53	7.419%	$227.2234	$227.22	$227.20	$227.20
Purchase #2	$26.27	8.730%	$28.5634	$28.56	$28.55	$28.60
Purchase #3	$222.73	4.106%	$231.8753	$231.88	$231.90	$231.90
Purchase #4	$171.28	4.648%	$179.2411	$179.24	$179.25	$179.20
Purchase #5	$133.55	4.420%	$139.4529	$139.45	$139.45	$139.50
Purchase #6	$29.91	4.493%	$31.2539	$31.25	$31.25	$31.30
Purchase #7	$25.89	7.223%	$27.76	$27.76	$27.75	$27.80
7 purchase totals =	$821.16		$865.3700	$865.36	$865.35	$865.50