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	$133.73	10.171%	$147.3317	$147.33	$147.35	$147.30
Purchase #2	$9.95	5.357%	$10.483	$10.48	$10.50	$10.50
Purchase #3	$29.44	7.272%	$31.5809	$31.58	$31.60	$31.60
Purchase #4	$247.32	6.636%	$263.7322	$263.73	$263.75	$263.70
Purchase #5	$191.45	10.490%	$211.5331	$211.53	$211.55	$211.50
Purchase #6	$89.83	10.832%	$99.5604	$99.56	$99.55	$99.60
Purchase #7	$213.59	3.704%	$221.5014	$221.50	$221.50	$221.50
7 purchase totals =	$915.31		$985.7227	$985.71	$985.80	$985.70