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	$71.79	5.265%	$75.5697	$75.57	$75.55	$75.60
Purchase #2	$207.73	13.420%	$235.6074	$235.61	$235.60	$235.60
Purchase #3	$80.41	11.327%	$89.518	$89.52	$89.50	$89.50
Purchase #4	$206.33	13.754%	$234.7086	$234.71	$234.70	$234.70
Purchase #5	$122.94	4.371%	$128.3137	$128.31	$128.30	$128.30
Purchase #6	$233.64	12.778%	$263.4945	$263.49	$263.50	$263.50
Purchase #7	$42.82	6.860%	$45.7575	$45.76	$45.75	$45.80
7 purchase totals =	$965.66		$1,072.9694	$1,072.97	$1,072.90	$1,073.00