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	$148.56	12.733%	$167.4761	$167.48	$167.50	$167.50
Purchase #2	$238.31	10.595%	$263.5589	$263.56	$263.55	$263.60
Purchase #3	$123.32	5.386%	$129.962	$129.96	$129.95	$130.00
Purchase #4	$50.53	6.415%	$53.7715	$53.77	$53.75	$53.80
Purchase #5	$66.32	8.689%	$72.0825	$72.08	$72.10	$72.10
Purchase #6	$221.39	6.268%	$235.2667	$235.27	$235.25	$235.30
Purchase #7	$72.83	10.372%	$80.3839	$80.38	$80.40	$80.40
7 purchase totals =	$921.26		$1,002.5016	$1,002.50	$1,002.50	$1,002.70