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	$215.52	7.298%	$231.2486	$231.25	$231.25	$231.20
Purchase #2	$127.30	5.190%	$133.9069	$133.91	$133.90	$133.90
Purchase #3	$199.29	7.663%	$214.5616	$214.56	$214.55	$214.60
Purchase #4	$239.69	10.168%	$264.0617	$264.06	$264.05	$264.10
Purchase #5	$212.60	10.310%	$234.5191	$234.52	$234.50	$234.50
Purchase #6	$109.97	4.411%	$114.8208	$114.82	$114.80	$114.80
Purchase #7	$242.48	5.369%	$255.4988	$255.50	$255.50	$255.50
7 purchase totals =	$1,346.85		$1,448.6175	$1,448.62	$1,448.55	$1,448.60