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	$152.40	3.126%	$157.164	$157.16	$157.15	$157.20
Purchase #2	$232.50	5.773%	$245.9222	$245.92	$245.90	$245.90
Purchase #3	$242.35	12.214%	$271.9506	$271.95	$271.95	$272.00
Purchase #4	$56.73	7.693%	$61.0942	$61.09	$61.10	$61.10
Purchase #5	$134.57	5.146%	$141.495	$141.50	$141.50	$141.50
Purchase #6	$29.58	6.689%	$31.5586	$31.56	$31.55	$31.60
Purchase #7	$231.59	5.131%	$243.4729	$243.47	$243.45	$243.50
7 purchase totals =	$1,079.72		$1,152.6575	$1,152.65	$1,152.60	$1,152.80