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	$158.95	4.412%	$165.9629	$165.96	$165.95	$166.00
Purchase #2	$130.40	13.266%	$147.6989	$147.70	$147.70	$147.70
Purchase #3	$142.67	3.813%	$148.11	$148.11	$148.10	$148.10
Purchase #4	$93.39	13.194%	$105.7119	$105.71	$105.70	$105.70
Purchase #5	$97.99	6.702%	$104.5573	$104.56	$104.55	$104.60
Purchase #6	$168.94	13.487%	$191.7249	$191.72	$191.70	$191.70
Purchase #7	$248.37	6.107%	$263.538	$263.54	$263.55	$263.50
7 purchase totals =	$1,040.71		$1,127.3039	$1,127.30	$1,127.25	$1,127.30