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	$171.85	7.763%	$185.1907	$185.19	$185.20	$185.20
Purchase #2	$55.53	11.152%	$61.7227	$61.72	$61.70	$61.70
Purchase #3	$145.62	7.762%	$156.923	$156.92	$156.90	$156.90
Purchase #4	$81.82	11.465%	$91.2007	$91.20	$91.20	$91.20
Purchase #5	$85.46	9.210%	$93.3309	$93.33	$93.35	$93.30
Purchase #6	$84.79	13.663%	$96.3749	$96.37	$96.35	$96.40
Purchase #7	$25.91	6.287%	$27.539	$27.54	$27.55	$27.50
7 purchase totals =	$650.98		$712.2819	$712.27	$712.25	$712.20