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	$102.32	4.646%	$107.0738	$107.07	$107.05	$107.10
Purchase #2	$233.59	7.164%	$250.3244	$250.32	$250.30	$250.30
Purchase #3	$204.42	7.283%	$219.3079	$219.31	$219.30	$219.30
Purchase #4	$38.72	9.679%	$42.4677	$42.47	$42.45	$42.50
Purchase #5	$26.83	4.472%	$28.0298	$28.03	$28.05	$28.00
Purchase #6	$30.51	5.222%	$32.1032	$32.10	$32.10	$32.10
Purchase #7	$75.61	4.858%	$79.2831	$79.28	$79.30	$79.30
7 purchase totals =	$712.00		$758.5899	$758.58	$758.55	$758.60