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	$86.91	8.537%	$94.3295	$94.33	$94.35	$94.30
Purchase #2	$50.94	5.762%	$53.8752	$53.88	$53.90	$53.90
Purchase #3	$211.73	10.169%	$233.2608	$233.26	$233.25	$233.30
Purchase #4	$110.36	13.318%	$125.0577	$125.06	$125.05	$125.10
Purchase #5	$121.48	9.598%	$133.1397	$133.14	$133.15	$133.10
Purchase #6	$38.41	10.603%	$42.4826	$42.48	$42.50	$42.50
Purchase #7	$81.65	9.196%	$89.1585	$89.16	$89.15	$89.20
7 purchase totals =	$701.48		$771.3040	$771.31	$771.35	$771.40