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	$145.91	10.449%	$161.1561	$161.16	$161.15	$161.20
Purchase #2	$225.26	11.125%	$250.3202	$250.32	$250.30	$250.30
Purchase #3	$127.71	10.460%	$141.0685	$141.07	$141.05	$141.10
Purchase #4	$79.91	3.851%	$82.9873	$82.99	$83.00	$83.00
Purchase #5	$92.55	11.349%	$103.0535	$103.05	$103.05	$103.10
Purchase #6	$190.92	11.502%	$212.8796	$212.88	$212.90	$212.90
Purchase #7	$96.83	7.803%	$104.3856	$104.39	$104.40	$104.40
7 purchase totals =	$959.09		$1,055.8508	$1,055.86	$1,055.85	$1,056.00