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	$66.48	11.281%	$73.9796	$73.98	$74.00	$74.00
Purchase #2	$14.25	9.199%	$15.5609	$15.56	$15.55	$15.60
Purchase #3	$192.63	8.813%	$209.6065	$209.61	$209.60	$209.60
Purchase #4	$179.92	6.298%	$191.2514	$191.25	$191.25	$191.30
Purchase #5	$148.78	13.799%	$169.3102	$169.31	$169.30	$169.30
Purchase #6	$65.59	9.773%	$72.0001	$72.00	$72.00	$72.00
Purchase #7	$93.34	7.600%	$100.4338	$100.43	$100.45	$100.40
7 purchase totals =	$760.99		$832.1425	$832.14	$832.15	$832.20