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	$236.96	7.407%	$254.5116	$254.51	$254.50	$254.50
Purchase #2	$227.43	12.695%	$256.3022	$256.30	$256.30	$256.30
Purchase #3	$90.75	9.401%	$99.2814	$99.28	$99.30	$99.30
Purchase #4	$215.56	4.321%	$224.8743	$224.87	$224.85	$224.90
Purchase #5	$184.26	11.540%	$205.5236	$205.52	$205.50	$205.50
Purchase #6	$68.49	4.373%	$71.4851	$71.49	$71.50	$71.50
Purchase #7	$56.79	10.519%	$62.7637	$62.76	$62.75	$62.80
7 purchase totals =	$1,080.24		$1,174.7419	$1,174.73	$1,174.70	$1,174.80