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	$245.33	12.587%	$276.2097	$276.21	$276.20	$276.20
Purchase #2	$64.30	4.860%	$67.425	$67.43	$67.45	$67.40
Purchase #3	$81.52	10.213%	$89.8456	$89.85	$89.85	$89.80
Purchase #4	$210.90	5.847%	$223.2313	$223.23	$223.25	$223.20
Purchase #5	$184.86	3.651%	$191.6092	$191.61	$191.60	$191.60
Purchase #6	$196.57	5.379%	$207.1435	$207.14	$207.15	$207.10
Purchase #7	$16.83	13.536%	$19.1081	$19.11	$19.10	$19.10
7 purchase totals =	$1,000.31		$1,074.5724	$1,074.58	$1,074.60	$1,074.40