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	$70.60	10.653%	$78.121	$78.12	$78.10	$78.10
Purchase #2	$17.47	3.799%	$18.1337	$18.13	$18.15	$18.10
Purchase #3	$171.68	10.536%	$189.7682	$189.77	$189.75	$189.80
Purchase #4	$183.94	8.421%	$199.4296	$199.43	$199.45	$199.40
Purchase #5	$140.90	5.310%	$148.3818	$148.38	$148.40	$148.40
Purchase #6	$232.76	5.466%	$245.4827	$245.48	$245.50	$245.50
Purchase #7	$192.62	12.354%	$216.4163	$216.42	$216.40	$216.40
7 purchase totals =	$1,009.97		$1,095.7333	$1,095.73	$1,095.75	$1,095.70