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	$127.32	5.171%	$133.9037	$133.90	$133.90	$133.90
Purchase #2	$205.95	6.443%	$219.2194	$219.22	$219.20	$219.20
Purchase #3	$95.82	11.132%	$106.4867	$106.49	$106.50	$106.50
Purchase #4	$58.50	7.333%	$62.7898	$62.79	$62.80	$62.80
Purchase #5	$234.35	10.871%	$259.8262	$259.83	$259.85	$259.80
Purchase #6	$147.58	5.343%	$155.4652	$155.47	$155.45	$155.50
Purchase #7	$139.81	6.607%	$149.0472	$149.05	$149.05	$149.00
7 purchase totals =	$1,009.33		$1,086.7382	$1,086.75	$1,086.75	$1,086.70