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	$161.69	4.213%	$168.502	$168.50	$168.50	$168.50
Purchase #2	$224.63	9.795%	$246.6325	$246.63	$246.65	$246.60
Purchase #3	$63.86	5.700%	$67.5	$67.50	$67.50	$67.50
Purchase #4	$49.85	11.501%	$55.5832	$55.58	$55.60	$55.60
Purchase #5	$111.91	7.472%	$120.2719	$120.27	$120.25	$120.30
Purchase #6	$219.48	6.187%	$233.0592	$233.06	$233.05	$233.10
Purchase #7	$148.74	13.746%	$169.1858	$169.19	$169.20	$169.20
7 purchase totals =	$980.16		$1,060.7346	$1,060.73	$1,060.75	$1,060.80