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	$188.28	11.767%	$210.4349	$210.43	$210.45	$210.40
Purchase #2	$62.60	11.503%	$69.8009	$69.80	$69.80	$69.80
Purchase #3	$60.42	7.640%	$65.0361	$65.04	$65.05	$65.00
Purchase #4	$228.45	9.604%	$250.3903	$250.39	$250.40	$250.40
Purchase #5	$113.74	11.684%	$127.0294	$127.03	$127.05	$127.00
Purchase #6	$56.55	3.512%	$58.536	$58.54	$58.55	$58.50
Purchase #7	$90.60	10.378%	$100.0025	$100.00	$100.00	$100.00
7 purchase totals =	$800.64		$881.2301	$881.23	$881.30	$881.10