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	$160.74	12.409%	$180.6862	$180.69	$180.70	$180.70
Purchase #2	$245.88	11.284%	$273.6251	$273.63	$273.65	$273.60
Purchase #3	$215.73	4.639%	$225.7377	$225.74	$225.75	$225.70
Purchase #4	$38.57	4.443%	$40.2837	$40.28	$40.30	$40.30
Purchase #5	$142.38	9.812%	$156.3503	$156.35	$156.35	$156.40
Purchase #6	$204.33	12.755%	$230.3923	$230.39	$230.40	$230.40
Purchase #7	$35.89	3.306%	$37.0765	$37.08	$37.10	$37.10
7 purchase totals =	$1,043.52		$1,144.1518	$1,144.16	$1,144.25	$1,144.20