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	$23.85	5.633%	$25.1935	$25.19	$25.20	$25.20
Purchase #2	$103.79	5.572%	$109.5732	$109.57	$109.55	$109.60
Purchase #3	$95.44	10.489%	$105.4507	$105.45	$105.45	$105.50
Purchase #4	$240.47	12.179%	$269.7568	$269.76	$269.75	$269.80
Purchase #5	$152.25	3.543%	$157.6442	$157.64	$157.65	$157.60
Purchase #6	$182.77	8.420%	$198.1592	$198.16	$198.15	$198.20
Purchase #7	$131.74	7.443%	$141.5454	$141.55	$141.55	$141.50
7 purchase totals =	$930.31		$1,007.3230	$1,007.32	$1,007.30	$1,007.40