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	$168.81	11.505%	$188.2316	$188.23	$188.25	$188.20
Purchase #2	$144.30	11.335%	$160.6564	$160.66	$160.65	$160.70
Purchase #3	$96.62	12.297%	$108.5014	$108.50	$108.50	$108.50
Purchase #4	$238.70	7.246%	$255.9962	$256.00	$256.00	$256.00
Purchase #5	$91.54	11.476%	$102.0451	$102.05	$102.05	$102.00
Purchase #6	$93.47	7.700%	$100.6672	$100.67	$100.65	$100.70
Purchase #7	$79.46	8.714%	$86.3841	$86.38	$86.40	$86.40
7 purchase totals =	$912.90		$1,002.4820	$1,002.49	$1,002.50	$1,002.50