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	$223.42	7.718%	$240.6636	$240.66	$240.65	$240.70
Purchase #2	$55.58	6.184%	$59.0171	$59.02	$59.00	$59.00
Purchase #3	$46.45	5.746%	$49.119	$49.12	$49.10	$49.10
Purchase #4	$233.66	7.181%	$250.4391	$250.44	$250.45	$250.40
Purchase #5	$95.99	9.705%	$105.3058	$105.31	$105.30	$105.30
Purchase #6	$237.48	7.730%	$255.8372	$255.84	$255.85	$255.80
Purchase #7	$142.88	8.718%	$155.3363	$155.34	$155.35	$155.30
7 purchase totals =	$1,035.46		$1,115.7181	$1,115.73	$1,115.70	$1,115.60