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	$91.89	4.547%	$96.0682	$96.07	$96.05	$96.10
Purchase #2	$145.88	7.115%	$156.2594	$156.26	$156.25	$156.30
Purchase #3	$169.61	9.638%	$185.957	$185.96	$185.95	$186.00
Purchase #4	$37.29	6.817%	$39.8321	$39.83	$39.85	$39.80
Purchase #5	$176.83	4.420%	$184.6459	$184.65	$184.65	$184.60
Purchase #6	$150.62	12.566%	$169.5469	$169.55	$169.55	$169.50
Purchase #7	$196.83	6.295%	$209.2204	$209.22	$209.20	$209.20
7 purchase totals =	$968.95		$1,041.5299	$1,041.54	$1,041.50	$1,041.50