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	$208.35	4.634%	$218.0049	$218.00	$218.00	$218.00
Purchase #2	$136.86	4.479%	$142.99	$142.99	$143.00	$143.00
Purchase #3	$96.33	3.461%	$99.664	$99.66	$99.65	$99.70
Purchase #4	$116.76	5.677%	$123.3885	$123.39	$123.40	$123.40
Purchase #5	$100.66	13.367%	$114.1152	$114.12	$114.10	$114.10
Purchase #6	$218.48	3.308%	$225.7073	$225.71	$225.70	$225.70
Purchase #7	$128.76	10.490%	$142.2669	$142.27	$142.25	$142.30
7 purchase totals =	$1,006.20		$1,066.1368	$1,066.14	$1,066.10	$1,066.20