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	$115.88	7.506%	$124.578	$124.58	$124.60	$124.60
Purchase #2	$85.74	7.168%	$91.8858	$91.89	$91.90	$91.90
Purchase #3	$104.72	5.792%	$110.7854	$110.79	$110.80	$110.80
Purchase #4	$5.83	7.671%	$6.2772	$6.28	$6.30	$6.30
Purchase #5	$64.27	4.730%	$67.31	$67.31	$67.30	$67.30
Purchase #6	$241.39	4.288%	$251.7408	$251.74	$251.75	$251.70
Purchase #7	$138.93	3.816%	$144.2316	$144.23	$144.25	$144.20
7 purchase totals =	$756.76		$796.8088	$796.82	$796.90	$796.80