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	$233.82	4.346%	$243.9818	$243.98	$244.00	$244.00
Purchase #2	$209.77	4.169%	$218.5153	$218.52	$218.50	$218.50
Purchase #3	$238.67	11.277%	$265.5848	$265.58	$265.60	$265.60
Purchase #4	$118.55	11.498%	$132.1809	$132.18	$132.20	$132.20
Purchase #5	$34.38	11.454%	$38.3179	$38.32	$38.30	$38.30
Purchase #6	$37.50	8.405%	$40.6519	$40.65	$40.65	$40.70
Purchase #7	$117.96	11.293%	$131.2812	$131.28	$131.30	$131.30
7 purchase totals =	$990.65		$1,070.5138	$1,070.51	$1,070.55	$1,070.60