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	$249.27	7.158%	$267.1127	$267.11	$267.10	$267.10
Purchase #2	$165.97	5.317%	$174.7946	$174.79	$174.80	$174.80
Purchase #3	$150.38	10.751%	$166.5474	$166.55	$166.55	$166.50
Purchase #4	$185.88	10.525%	$205.4439	$205.44	$205.45	$205.40
Purchase #5	$85.28	5.303%	$89.8024	$89.80	$89.80	$89.80
Purchase #6	$64.93	5.142%	$68.2687	$68.27	$68.25	$68.30
Purchase #7	$65.93	5.123%	$69.3076	$69.31	$69.30	$69.30
7 purchase totals =	$967.64		$1,041.2773	$1,041.27	$1,041.25	$1,041.20