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	$65.83	7.170%	$70.55	$70.55	$70.55	$70.60
Purchase #2	$152.28	6.410%	$162.0411	$162.04	$162.05	$162.00
Purchase #3	$54.79	5.290%	$57.6884	$57.69	$57.70	$57.70
Purchase #4	$97.80	11.773%	$109.314	$109.31	$109.30	$109.30
Purchase #5	$148.52	5.852%	$157.2114	$157.21	$157.20	$157.20
Purchase #6	$40.90	10.195%	$45.0698	$45.07	$45.05	$45.10
Purchase #7	$67.47	5.764%	$71.359	$71.36	$71.35	$71.40
7 purchase totals =	$627.59		$673.2337	$673.23	$673.20	$673.30