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	$132.62	7.264%	$142.2535	$142.25	$142.25	$142.30
Purchase #2	$83.70	10.746%	$92.6944	$92.69	$92.70	$92.70
Purchase #3	$141.61	6.303%	$150.5357	$150.54	$150.55	$150.50
Purchase #4	$180.59	4.264%	$188.2904	$188.29	$188.30	$188.30
Purchase #5	$197.42	5.449%	$208.1774	$208.18	$208.20	$208.20
Purchase #6	$156.49	10.611%	$173.0952	$173.10	$173.10	$173.10
Purchase #7	$89.26	7.344%	$95.8153	$95.82	$95.80	$95.80
7 purchase totals =	$981.69		$1,050.8619	$1,050.87	$1,050.90	$1,050.90