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	$62.79	11.134%	$69.781	$69.78	$69.80	$69.80
Purchase #2	$201.47	13.393%	$228.4529	$228.45	$228.45	$228.50
Purchase #3	$247.32	11.561%	$275.9127	$275.91	$275.90	$275.90
Purchase #4	$78.33	5.717%	$82.8081	$82.81	$82.80	$82.80
Purchase #5	$59.44	6.530%	$63.3214	$63.32	$63.30	$63.30
Purchase #6	$137.99	10.424%	$152.3741	$152.37	$152.35	$152.40
Purchase #7	$182.62	3.297%	$188.641	$188.64	$188.65	$188.60
7 purchase totals =	$969.96		$1,061.2912	$1,061.28	$1,061.25	$1,061.30