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	$119.71	9.804%	$131.4464	$131.45	$131.45	$131.40
Purchase #2	$45.28	13.535%	$51.4086	$51.41	$51.40	$51.40
Purchase #3	$59.69	4.137%	$62.1594	$62.16	$62.15	$62.20
Purchase #4	$243.73	9.631%	$267.2036	$267.20	$267.20	$267.20
Purchase #5	$74.71	7.519%	$80.3274	$80.33	$80.35	$80.30
Purchase #6	$29.86	12.398%	$33.562	$33.56	$33.55	$33.60
Purchase #7	$95.67	8.496%	$103.7981	$103.80	$103.80	$103.80
7 purchase totals =	$668.65		$729.9055	$729.91	$729.90	$729.90