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	$47.71	6.163%	$50.6504	$50.65	$50.65	$50.70
Purchase #2	$38.35	5.531%	$40.4711	$40.47	$40.45	$40.50
Purchase #3	$116.54	3.477%	$120.5921	$120.59	$120.60	$120.60
Purchase #4	$126.97	10.774%	$140.6497	$140.65	$140.65	$140.60
Purchase #5	$179.69	3.130%	$185.3143	$185.31	$185.30	$185.30
Purchase #6	$192.88	6.815%	$206.0248	$206.02	$206.00	$206.00
Purchase #7	$246.36	11.793%	$275.4132	$275.41	$275.40	$275.40
7 purchase totals =	$948.50		$1,019.1156	$1,019.10	$1,019.05	$1,019.10