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	$41.56	5.155%	$43.7024	$43.70	$43.70	$43.70
Purchase #2	$223.32	12.316%	$250.8241	$250.82	$250.80	$250.80
Purchase #3	$76.62	11.846%	$85.6964	$85.70	$85.70	$85.70
Purchase #4	$10.34	11.631%	$11.5426	$11.54	$11.55	$11.50
Purchase #5	$248.77	13.302%	$281.8614	$281.86	$281.85	$281.90
Purchase #6	$6.53	9.303%	$7.1375	$7.14	$7.15	$7.10
Purchase #7	$85.93	9.399%	$94.0066	$94.01	$94.00	$94.00
7 purchase totals =	$693.07		$774.7710	$774.77	$774.75	$774.70