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	$64.74	11.103%	$71.9281	$71.93	$71.95	$71.90
Purchase #2	$246.55	12.486%	$277.3342	$277.33	$277.35	$277.30
Purchase #3	$33.27	13.669%	$37.8177	$37.82	$37.80	$37.80
Purchase #4	$177.92	3.626%	$184.3714	$184.37	$184.35	$184.40
Purchase #5	$219.91	13.808%	$250.2752	$250.28	$250.30	$250.30
Purchase #6	$42.92	11.654%	$47.9219	$47.92	$47.90	$47.90
Purchase #7	$147.75	13.140%	$167.1644	$167.16	$167.15	$167.20
7 purchase totals =	$933.06		$1,036.8129	$1,036.81	$1,036.80	$1,036.80