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	$40.41	13.310%	$45.7886	$45.79	$45.80	$45.80
Purchase #2	$114.74	11.504%	$127.9397	$127.94	$127.95	$127.90
Purchase #3	$61.48	13.195%	$69.5923	$69.59	$69.60	$69.60
Purchase #4	$99.35	8.315%	$107.611	$107.61	$107.60	$107.60
Purchase #5	$242.90	3.801%	$252.1326	$252.13	$252.15	$252.10
Purchase #6	$180.45	5.517%	$190.4054	$190.41	$190.40	$190.40
Purchase #7	$191.80	10.440%	$211.8239	$211.82	$211.80	$211.80
7 purchase totals =	$931.13		$1,005.2935	$1,005.29	$1,005.30	$1,005.20