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	$123.32	7.374%	$132.4136	$132.41	$132.40	$132.40
Purchase #2	$219.98	13.862%	$250.4736	$250.47	$250.45	$250.50
Purchase #3	$35.60	9.764%	$39.076	$39.08	$39.10	$39.10
Purchase #4	$73.80	11.151%	$82.0294	$82.03	$82.05	$82.00
Purchase #5	$180.53	4.629%	$188.8867	$188.89	$188.90	$188.90
Purchase #6	$225.85	6.663%	$240.8984	$240.90	$240.90	$240.90
Purchase #7	$69.95	4.862%	$73.351	$73.35	$73.35	$73.40
7 purchase totals =	$929.03		$1,007.1287	$1,007.13	$1,007.15	$1,007.20