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	$29.87	9.856%	$32.814	$32.81	$32.80	$32.80
Purchase #2	$28.82	9.666%	$31.6057	$31.61	$31.60	$31.60
Purchase #3	$93.33	12.243%	$104.7564	$104.76	$104.75	$104.80
Purchase #4	$90.31	3.186%	$93.1873	$93.19	$93.20	$93.20
Purchase #5	$174.41	5.616%	$184.2049	$184.20	$184.20	$184.20
Purchase #6	$88.46	11.400%	$98.5444	$98.54	$98.55	$98.50
Purchase #7	$59.39	4.829%	$62.2579	$62.26	$62.25	$62.30
7 purchase totals =	$564.59		$607.3706	$607.37	$607.35	$607.40