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	$228.26	13.327%	$258.6802	$258.68	$258.70	$258.70
Purchase #2	$81.89	9.588%	$89.7416	$89.74	$89.75	$89.70
Purchase #3	$64.48	4.310%	$67.2591	$67.26	$67.25	$67.30
Purchase #4	$53.89	6.712%	$57.5071	$57.51	$57.50	$57.50
Purchase #5	$208.36	13.182%	$235.826	$235.83	$235.85	$235.80
Purchase #6	$222.25	3.596%	$230.2421	$230.24	$230.25	$230.20
Purchase #7	$123.62	3.295%	$127.6933	$127.69	$127.70	$127.70
7 purchase totals =	$982.75		$1,066.9494	$1,066.95	$1,067.00	$1,066.90