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	$183.28	10.164%	$201.9086	$201.91	$201.90	$201.90
Purchase #2	$143.32	9.260%	$156.5914	$156.59	$156.60	$156.60
Purchase #3	$235.72	3.144%	$243.131	$243.13	$243.15	$243.10
Purchase #4	$36.45	3.690%	$37.795	$37.80	$37.80	$37.80
Purchase #5	$13.88	7.436%	$14.9121	$14.91	$14.90	$14.90
Purchase #6	$18.91	12.589%	$21.2906	$21.29	$21.30	$21.30
Purchase #7	$79.91	3.497%	$82.7045	$82.70	$82.70	$82.70
7 purchase totals =	$711.47		$758.3332	$758.33	$758.35	$758.30