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	$87.70	9.109%	$95.6886	$95.69	$95.70	$95.70
Purchase #2	$188.70	7.821%	$203.4582	$203.46	$203.45	$203.50
Purchase #3	$185.40	6.262%	$197.0097	$197.01	$197.00	$197.00
Purchase #4	$98.46	4.690%	$103.0778	$103.08	$103.10	$103.10
Purchase #5	$47.75	12.661%	$53.7956	$53.80	$53.80	$53.80
Purchase #6	$43.48	11.688%	$48.5619	$48.56	$48.55	$48.60
Purchase #7	$56.83	4.801%	$59.5584	$59.56	$59.55	$59.60
7 purchase totals =	$708.32		$761.1502	$761.16	$761.15	$761.30