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	$218.91	11.542%	$244.1766	$244.18	$244.20	$244.20
Purchase #2	$217.32	13.147%	$245.8911	$245.89	$245.90	$245.90
Purchase #3	$85.99	4.210%	$89.6102	$89.61	$89.60	$89.60
Purchase #4	$217.64	3.739%	$225.7776	$225.78	$225.80	$225.80
Purchase #5	$57.60	6.846%	$61.5433	$61.54	$61.55	$61.50
Purchase #6	$207.75	10.479%	$229.5201	$229.52	$229.50	$229.50
Purchase #7	$125.90	12.502%	$141.64	$141.64	$141.65	$141.60
7 purchase totals =	$1,131.11		$1,238.1589	$1,238.16	$1,238.20	$1,238.10