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	$188.39	9.211%	$205.7426	$205.74	$205.75	$205.70
Purchase #2	$19.33	9.205%	$21.1093	$21.11	$21.10	$21.10
Purchase #3	$216.84	3.108%	$223.5794	$223.58	$223.60	$223.60
Purchase #4	$170.31	12.275%	$191.2156	$191.22	$191.20	$191.20
Purchase #5	$59.55	7.661%	$64.1121	$64.11	$64.10	$64.10
Purchase #6	$205.50	8.761%	$223.5039	$223.50	$223.50	$223.50
Purchase #7	$151.45	7.401%	$162.6588	$162.66	$162.65	$162.70
7 purchase totals =	$1,011.37		$1,091.9217	$1,091.92	$1,091.90	$1,091.90