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	$200.96	8.156%	$217.3503	$217.35	$217.35	$217.40
Purchase #2	$166.97	4.782%	$174.9545	$174.95	$174.95	$175.00
Purchase #3	$29.75	10.587%	$32.8996	$32.90	$32.90	$32.90
Purchase #4	$54.56	9.671%	$59.8365	$59.84	$59.85	$59.80
Purchase #5	$169.85	10.872%	$188.3161	$188.32	$188.30	$188.30
Purchase #6	$156.41	6.248%	$166.1825	$166.18	$166.20	$166.20
Purchase #7	$79.28	9.123%	$86.5127	$86.51	$86.50	$86.50
7 purchase totals =	$857.78		$926.0522	$926.05	$926.05	$926.10