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	$70.57	3.782%	$73.239	$73.24	$73.25	$73.20
Purchase #2	$91.73	9.205%	$100.1737	$100.17	$100.15	$100.20
Purchase #3	$217.61	4.380%	$227.1413	$227.14	$227.15	$227.10
Purchase #4	$10.91	7.729%	$11.7532	$11.75	$11.75	$11.80
Purchase #5	$80.90	12.276%	$90.8313	$90.83	$90.85	$90.80
Purchase #6	$94.93	9.640%	$104.0813	$104.08	$104.10	$104.10
Purchase #7	$240.90	12.586%	$271.2197	$271.22	$271.20	$271.20
7 purchase totals =	$807.55		$878.4395	$878.43	$878.45	$878.40