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	$47.90	13.196%	$54.2209	$54.22	$54.20	$54.20
Purchase #2	$191.87	10.565%	$212.1411	$212.14	$212.15	$212.10
Purchase #3	$55.78	9.473%	$61.064	$61.06	$61.05	$61.10
Purchase #4	$233.39	3.533%	$241.6357	$241.64	$241.65	$241.60
Purchase #5	$222.62	12.625%	$250.7258	$250.73	$250.75	$250.70
Purchase #6	$212.85	6.369%	$226.4064	$226.41	$226.40	$226.40
Purchase #7	$96.77	8.299%	$104.8009	$104.80	$104.80	$104.80
7 purchase totals =	$1,061.18		$1,150.9948	$1,151.00	$1,151.00	$1,150.90