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	$211.40	11.165%	$235.0028	$235.00	$235.00	$235.00
Purchase #2	$115.48	10.587%	$127.7059	$127.71	$127.70	$127.70
Purchase #3	$164.38	9.569%	$180.1095	$180.11	$180.10	$180.10
Purchase #4	$94.34	9.643%	$103.4372	$103.44	$103.45	$103.40
Purchase #5	$99.89	3.227%	$103.1135	$103.11	$103.10	$103.10
Purchase #6	$33.90	4.426%	$35.4004	$35.40	$35.40	$35.40
Purchase #7	$147.98	8.399%	$160.4088	$160.41	$160.40	$160.40
7 purchase totals =	$867.37		$945.1781	$945.18	$945.15	$945.10