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	$244.95	4.843%	$256.8129	$256.81	$256.80	$256.80
Purchase #2	$121.80	4.540%	$127.3297	$127.33	$127.35	$127.30
Purchase #3	$211.76	6.690%	$225.9267	$225.93	$225.95	$225.90
Purchase #4	$193.33	11.648%	$215.8491	$215.85	$215.85	$215.80
Purchase #5	$166.25	11.846%	$185.944	$185.94	$185.95	$185.90
Purchase #6	$100.39	6.140%	$106.5539	$106.55	$106.55	$106.60
Purchase #7	$44.53	13.614%	$50.5923	$50.59	$50.60	$50.60
7 purchase totals =	$1,083.01		$1,169.0086	$1,169.00	$1,169.05	$1,168.90