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	$107.35	5.181%	$112.9118	$112.91	$112.90	$112.90
Purchase #2	$154.73	13.461%	$175.5582	$175.56	$175.55	$175.60
Purchase #3	$206.51	3.152%	$213.0192	$213.02	$213.00	$213.00
Purchase #4	$177.44	12.398%	$199.439	$199.44	$199.45	$199.40
Purchase #5	$81.71	8.788%	$88.8907	$88.89	$88.90	$88.90
Purchase #6	$58.89	4.123%	$61.318	$61.32	$61.30	$61.30
Purchase #7	$145.33	4.844%	$152.3698	$152.37	$152.35	$152.40
7 purchase totals =	$931.96		$1,003.5067	$1,003.51	$1,003.45	$1,003.50