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	$90.42	11.316%	$100.6519	$100.65	$100.65	$100.70
Purchase #2	$176.44	13.774%	$200.7428	$200.74	$200.75	$200.70
Purchase #3	$123.37	5.648%	$130.3379	$130.34	$130.35	$130.30
Purchase #4	$184.75	3.612%	$191.4232	$191.42	$191.40	$191.40
Purchase #5	$15.66	4.234%	$16.323	$16.32	$16.30	$16.30
Purchase #6	$128.70	3.645%	$133.3911	$133.39	$133.40	$133.40
Purchase #7	$84.69	5.637%	$89.464	$89.46	$89.45	$89.50
7 purchase totals =	$804.03		$862.3339	$862.32	$862.30	$862.30