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	$143.85	5.616%	$151.9286	$151.93	$151.95	$151.90
Purchase #2	$234.56	5.477%	$247.4069	$247.41	$247.40	$247.40
Purchase #3	$215.68	12.851%	$243.397	$243.40	$243.40	$243.40
Purchase #4	$157.81	5.167%	$165.964	$165.96	$165.95	$166.00
Purchase #5	$94.67	6.450%	$100.7762	$100.78	$100.80	$100.80
Purchase #6	$241.56	3.820%	$250.7876	$250.79	$250.80	$250.80
Purchase #7	$115.96	10.183%	$127.7682	$127.77	$127.75	$127.80
7 purchase totals =	$1,204.09		$1,288.0285	$1,288.04	$1,288.05	$1,288.10