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	$76.72	8.842%	$83.5036	$83.50	$83.50	$83.50
Purchase #2	$66.36	5.521%	$70.0237	$70.02	$70.00	$70.00
Purchase #3	$61.94	12.686%	$69.7977	$69.80	$69.80	$69.80
Purchase #4	$59.45	13.653%	$67.5667	$67.57	$67.55	$67.60
Purchase #5	$36.91	10.709%	$40.8627	$40.86	$40.85	$40.90
Purchase #6	$67.77	6.646%	$72.274	$72.27	$72.25	$72.30
Purchase #7	$55.31	8.687%	$60.1148	$60.11	$60.10	$60.10
7 purchase totals =	$424.46		$464.1432	$464.13	$464.05	$464.20