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	$144.49	11.351%	$160.8911	$160.89	$160.90	$160.90
Purchase #2	$19.67	12.562%	$22.1409	$22.14	$22.15	$22.10
Purchase #3	$145.90	10.225%	$160.8183	$160.82	$160.80	$160.80
Purchase #4	$178.65	5.117%	$187.7915	$187.79	$187.80	$187.80
Purchase #5	$249.30	12.668%	$280.8813	$280.88	$280.90	$280.90
Purchase #6	$31.28	12.224%	$35.1037	$35.10	$35.10	$35.10
Purchase #7	$94.58	9.840%	$103.8867	$103.89	$103.90	$103.90
7 purchase totals =	$863.87		$951.5135	$951.51	$951.55	$951.50