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	$213.38	4.748%	$223.5113	$223.51	$223.50	$223.50
Purchase #2	$90.51	12.284%	$101.6282	$101.63	$101.65	$101.60
Purchase #3	$215.55	6.337%	$229.2094	$229.21	$229.20	$229.20
Purchase #4	$110.37	3.419%	$114.1436	$114.14	$114.15	$114.10
Purchase #5	$171.38	3.464%	$177.3166	$177.32	$177.30	$177.30
Purchase #6	$64.80	9.380%	$70.8782	$70.88	$70.90	$70.90
Purchase #7	$146.72	12.793%	$165.4899	$165.49	$165.50	$165.50
7 purchase totals =	$1,012.71		$1,082.1772	$1,082.18	$1,082.20	$1,082.10