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	$147.37	6.322%	$156.6867	$156.69	$156.70	$156.70
Purchase #2	$97.38	7.397%	$104.5832	$104.58	$104.60	$104.60
Purchase #3	$218.56	4.148%	$227.6259	$227.63	$227.65	$227.60
Purchase #4	$161.45	4.438%	$168.6152	$168.62	$168.60	$168.60
Purchase #5	$26.67	6.474%	$28.3966	$28.40	$28.40	$28.40
Purchase #6	$33.98	9.243%	$37.1208	$37.12	$37.10	$37.10
Purchase #7	$38.46	12.289%	$43.1863	$43.19	$43.20	$43.20
7 purchase totals =	$723.87		$766.2147	$766.23	$766.25	$766.20