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	$121.70	8.434%	$131.9642	$131.96	$131.95	$132.00
Purchase #2	$47.44	13.238%	$53.7201	$53.72	$53.70	$53.70
Purchase #3	$67.72	7.720%	$72.948	$72.95	$72.95	$72.90
Purchase #4	$29.56	3.740%	$30.6655	$30.67	$30.65	$30.70
Purchase #5	$25.28	9.682%	$27.7276	$27.73	$27.75	$27.70
Purchase #6	$23.89	13.723%	$27.1684	$27.17	$27.15	$27.20
Purchase #7	$93.41	6.744%	$99.7096	$99.71	$99.70	$99.70
7 purchase totals =	$409.00		$443.9034	$443.91	$443.85	$443.90