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	$106.74	7.577%	$114.8277	$114.83	$114.85	$114.80
Purchase #2	$213.93	5.111%	$224.864	$224.86	$224.85	$224.90
Purchase #3	$38.70	5.112%	$40.6783	$40.68	$40.70	$40.70
Purchase #4	$97.63	4.809%	$102.325	$102.33	$102.35	$102.30
Purchase #5	$28.69	11.297%	$31.9311	$31.93	$31.95	$31.90
Purchase #6	$165.72	9.439%	$181.3623	$181.36	$181.35	$181.40
Purchase #7	$138.41	5.860%	$146.5208	$146.52	$146.50	$146.50
7 purchase totals =	$789.82		$842.5092	$842.51	$842.55	$842.50