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	$73.49	11.266%	$81.7694	$81.77	$81.75	$81.80
Purchase #2	$62.72	11.409%	$69.8757	$69.88	$69.90	$69.90
Purchase #3	$168.49	10.142%	$185.5783	$185.58	$185.60	$185.60
Purchase #4	$8.53	5.719%	$9.0178	$9.02	$9.00	$9.00
Purchase #5	$215.86	13.246%	$244.4528	$244.45	$244.45	$244.50
Purchase #6	$152.58	12.872%	$172.2201	$172.22	$172.20	$172.20
Purchase #7	$231.69	9.333%	$253.3136	$253.31	$253.30	$253.30
7 purchase totals =	$913.36		$1,016.2277	$1,016.23	$1,016.20	$1,016.30