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	$91.67	12.654%	$103.2699	$103.27	$103.25	$103.30
Purchase #2	$118.53	5.661%	$125.24	$125.24	$125.25	$125.20
Purchase #3	$242.44	13.801%	$275.8991	$275.90	$275.90	$275.90
Purchase #4	$195.93	10.642%	$216.7809	$216.78	$216.80	$216.80
Purchase #5	$66.36	6.416%	$70.6177	$70.62	$70.60	$70.60
Purchase #6	$17.59	5.674%	$18.5881	$18.59	$18.60	$18.60
Purchase #7	$233.32	4.799%	$244.517	$244.52	$244.50	$244.50
7 purchase totals =	$965.84		$1,054.9127	$1,054.92	$1,054.90	$1,054.90