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	$137.88	10.850%	$152.84	$152.84	$152.85	$152.80
Purchase #2	$207.37	7.346%	$222.6034	$222.60	$222.60	$222.60
Purchase #3	$70.30	11.747%	$78.5581	$78.56	$78.55	$78.60
Purchase #4	$223.25	5.428%	$235.368	$235.37	$235.35	$235.40
Purchase #5	$91.96	7.302%	$98.6749	$98.67	$98.65	$98.70
Purchase #6	$139.96	7.253%	$150.1113	$150.11	$150.10	$150.10
Purchase #7	$62.33	7.336%	$66.9025	$66.90	$66.90	$66.90
7 purchase totals =	$933.05		$1,005.0582	$1,005.05	$1,005.00	$1,005.10