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	$108.87	6.213%	$115.6341	$115.63	$115.65	$115.60
Purchase #2	$105.31	9.855%	$115.6883	$115.69	$115.70	$115.70
Purchase #3	$135.76	12.315%	$152.4788	$152.48	$152.50	$152.50
Purchase #4	$29.57	6.456%	$31.479	$31.48	$31.50	$31.50
Purchase #5	$229.61	9.321%	$251.0119	$251.01	$251.00	$251.00
Purchase #6	$250.54	7.643%	$269.6888	$269.69	$269.70	$269.70
Purchase #7	$80.78	11.327%	$89.93	$89.93	$89.95	$89.90
7 purchase totals =	$940.44		$1,025.9109	$1,025.91	$1,026.00	$1,025.90