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	$134.89	12.493%	$151.7418	$151.74	$151.75	$151.70
Purchase #2	$196.54	12.102%	$220.3253	$220.33	$220.35	$220.30
Purchase #3	$196.41	11.155%	$218.3195	$218.32	$218.30	$218.30
Purchase #4	$98.91	4.683%	$103.542	$103.54	$103.55	$103.50
Purchase #5	$112.79	6.555%	$120.1834	$120.18	$120.20	$120.20
Purchase #6	$168.50	8.544%	$182.8966	$182.90	$182.90	$182.90
Purchase #7	$45.45	10.633%	$50.2827	$50.28	$50.30	$50.30
7 purchase totals =	$953.49		$1,047.2913	$1,047.29	$1,047.35	$1,047.20