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	$41.44	10.549%	$45.8115	$45.81	$45.80	$45.80
Purchase #2	$43.51	9.306%	$47.559	$47.56	$47.55	$47.60
Purchase #3	$78.77	8.572%	$85.5222	$85.52	$85.50	$85.50
Purchase #4	$46.86	9.786%	$51.4457	$51.45	$51.45	$51.40
Purchase #5	$89.90	10.580%	$99.4114	$99.41	$99.40	$99.40
Purchase #6	$73.64	5.632%	$77.7874	$77.79	$77.80	$77.80
Purchase #7	$200.69	9.845%	$220.4479	$220.45	$220.45	$220.40
7 purchase totals =	$574.81		$627.9851	$627.99	$627.95	$627.90