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	$40.66	12.438%	$45.7173	$45.72	$45.70	$45.70
Purchase #2	$234.29	12.746%	$264.1526	$264.15	$264.15	$264.20
Purchase #3	$75.46	6.674%	$80.4962	$80.50	$80.50	$80.50
Purchase #4	$157.71	13.476%	$178.963	$178.96	$178.95	$179.00
Purchase #5	$79.59	3.422%	$82.3136	$82.31	$82.30	$82.30
Purchase #6	$62.42	3.119%	$64.3669	$64.37	$64.35	$64.40
Purchase #7	$83.31	3.549%	$86.2667	$86.27	$86.25	$86.30
7 purchase totals =	$733.44		$802.2763	$802.28	$802.20	$802.40