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	$64.30	8.236%	$69.5957	$69.60	$69.60	$69.60
Purchase #2	$246.56	13.512%	$279.8752	$279.88	$279.90	$279.90
Purchase #3	$125.64	8.474%	$136.2867	$136.29	$136.30	$136.30
Purchase #4	$213.27	4.243%	$222.319	$222.32	$222.30	$222.30
Purchase #5	$134.76	6.797%	$143.9196	$143.92	$143.90	$143.90
Purchase #6	$67.88	3.752%	$70.4269	$70.43	$70.45	$70.40
Purchase #7	$102.38	3.258%	$105.7155	$105.72	$105.70	$105.70
7 purchase totals =	$954.79		$1,028.1386	$1,028.16	$1,028.15	$1,028.10