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	$197.87	6.172%	$210.0825	$210.08	$210.10	$210.10
Purchase #2	$213.65	4.653%	$223.5911	$223.59	$223.60	$223.60
Purchase #3	$99.42	4.317%	$103.712	$103.71	$103.70	$103.70
Purchase #4	$248.73	13.160%	$281.4629	$281.46	$281.45	$281.50
Purchase #5	$132.79	7.561%	$142.8303	$142.83	$142.85	$142.80
Purchase #6	$245.41	10.136%	$270.2848	$270.28	$270.30	$270.30
Purchase #7	$25.44	6.344%	$27.0539	$27.05	$27.05	$27.10
7 purchase totals =	$1,163.31		$1,259.0175	$1,259.00	$1,259.05	$1,259.10