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	$195.34	7.397%	$209.7893	$209.79	$209.80	$209.80
Purchase #2	$69.67	11.867%	$77.9377	$77.94	$77.95	$77.90
Purchase #3	$88.88	10.654%	$98.3493	$98.35	$98.35	$98.30
Purchase #4	$177.90	10.648%	$196.8428	$196.84	$196.85	$196.80
Purchase #5	$33.62	10.639%	$37.1968	$37.20	$37.20	$37.20
Purchase #6	$9.48	13.526%	$10.7623	$10.76	$10.75	$10.80
Purchase #7	$194.62	11.253%	$216.5206	$216.52	$216.50	$216.50
7 purchase totals =	$769.51		$847.3988	$847.40	$847.40	$847.30