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	$75.47	11.205%	$83.9264	$83.93	$83.95	$83.90
Purchase #2	$203.32	12.164%	$228.0518	$228.05	$228.05	$228.10
Purchase #3	$51.33	9.282%	$56.0945	$56.09	$56.10	$56.10
Purchase #4	$181.47	9.511%	$198.7296	$198.73	$198.75	$198.70
Purchase #5	$88.83	12.346%	$99.797	$99.80	$99.80	$99.80
Purchase #6	$99.67	11.744%	$111.3752	$111.38	$111.40	$111.40
Purchase #7	$9.62	4.841%	$10.0857	$10.09	$10.10	$10.10
7 purchase totals =	$709.71		$788.0602	$788.07	$788.15	$788.10