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	$221.88	3.307%	$229.2176	$229.22	$229.20	$229.20
Purchase #2	$245.70	4.135%	$255.8597	$255.86	$255.85	$255.90
Purchase #3	$223.34	8.156%	$241.5556	$241.56	$241.55	$241.60
Purchase #4	$104.49	6.488%	$111.2693	$111.27	$111.25	$111.30
Purchase #5	$15.34	11.238%	$17.0639	$17.06	$17.05	$17.10
Purchase #6	$13.36	13.114%	$15.112	$15.11	$15.10	$15.10
Purchase #7	$211.25	11.157%	$234.8192	$234.82	$234.80	$234.80
7 purchase totals =	$1,035.36		$1,104.8973	$1,104.90	$1,104.80	$1,105.00