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	$164.61	4.593%	$172.1705	$172.17	$172.15	$172.20
Purchase #2	$40.49	4.219%	$42.1983	$42.20	$42.20	$42.20
Purchase #3	$214.96	6.796%	$229.5687	$229.57	$229.55	$229.60
Purchase #4	$163.32	6.433%	$173.8264	$173.83	$173.85	$173.80
Purchase #5	$91.45	11.866%	$102.3015	$102.30	$102.30	$102.30
Purchase #6	$175.41	13.842%	$199.6903	$199.69	$199.70	$199.70
Purchase #7	$175.25	11.852%	$196.0206	$196.02	$196.00	$196.00
7 purchase totals =	$1,025.49		$1,115.7763	$1,115.78	$1,115.75	$1,115.80