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	$238.59	11.106%	$265.0878	$265.09	$265.10	$265.10
Purchase #2	$78.83	12.754%	$88.884	$88.88	$88.90	$88.90
Purchase #3	$131.28	13.587%	$149.117	$149.12	$149.10	$149.10
Purchase #4	$247.91	10.329%	$273.5166	$273.52	$273.50	$273.50
Purchase #5	$142.40	7.274%	$152.7582	$152.76	$152.75	$152.80
Purchase #6	$172.27	10.166%	$189.783	$189.78	$189.80	$189.80
Purchase #7	$11.43	12.456%	$12.8537	$12.85	$12.85	$12.90
7 purchase totals =	$1,022.71		$1,132.0003	$1,132.00	$1,132.00	$1,132.10