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	$227.30	4.136%	$236.7011	$236.70	$236.70	$236.70
Purchase #2	$7.92	3.321%	$8.183	$8.18	$8.20	$8.20
Purchase #3	$155.86	6.332%	$165.7291	$165.73	$165.75	$165.70
Purchase #4	$204.99	12.143%	$229.8819	$229.88	$229.90	$229.90
Purchase #5	$53.67	5.178%	$56.449	$56.45	$56.45	$56.40
Purchase #6	$78.52	13.716%	$89.2898	$89.29	$89.30	$89.30
Purchase #7	$250.40	5.679%	$264.6202	$264.62	$264.60	$264.60
7 purchase totals =	$978.66		$1,050.8541	$1,050.85	$1,050.90	$1,050.80