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	$128.30	10.301%	$141.5162	$141.52	$141.50	$141.50
Purchase #2	$210.62	7.263%	$225.9173	$225.92	$225.90	$225.90
Purchase #3	$147.98	5.699%	$156.4134	$156.41	$156.40	$156.40
Purchase #4	$42.52	3.189%	$43.876	$43.88	$43.90	$43.90
Purchase #5	$22.48	7.774%	$24.2276	$24.23	$24.25	$24.20
Purchase #6	$180.79	5.819%	$191.3102	$191.31	$191.30	$191.30
Purchase #7	$221.53	4.607%	$231.7359	$231.74	$231.75	$231.70
7 purchase totals =	$954.22		$1,014.9966	$1,015.01	$1,015.00	$1,014.90