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	$119.37	10.412%	$131.7988	$131.80	$131.80	$131.80
Purchase #2	$50.30	6.608%	$53.6238	$53.62	$53.60	$53.60
Purchase #3	$61.91	12.431%	$69.606	$69.61	$69.60	$69.60
Purchase #4	$250.69	13.474%	$284.468	$284.47	$284.45	$284.50
Purchase #5	$230.56	13.420%	$261.5012	$261.50	$261.50	$261.50
Purchase #6	$205.89	7.766%	$221.8794	$221.88	$221.90	$221.90
Purchase #7	$48.57	3.428%	$50.235	$50.24	$50.25	$50.20
7 purchase totals =	$967.29		$1,073.1122	$1,073.12	$1,073.10	$1,073.10