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	$153.25	6.192%	$162.7392	$162.74	$162.75	$162.70
Purchase #2	$83.85	6.642%	$89.4193	$89.42	$89.40	$89.40
Purchase #3	$238.82	11.413%	$266.0765	$266.08	$266.10	$266.10
Purchase #4	$209.65	7.215%	$224.7762	$224.78	$224.80	$224.80
Purchase #5	$183.50	3.502%	$189.9262	$189.93	$189.95	$189.90
Purchase #6	$203.29	9.421%	$222.442	$222.44	$222.45	$222.40
Purchase #7	$83.46	7.399%	$89.6352	$89.64	$89.65	$89.60
7 purchase totals =	$1,155.82		$1,245.0146	$1,245.03	$1,245.10	$1,244.90