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	$195.41	13.763%	$222.3043	$222.30	$222.30	$222.30
Purchase #2	$40.35	5.173%	$42.4373	$42.44	$42.45	$42.40
Purchase #3	$52.30	3.627%	$54.1969	$54.20	$54.20	$54.20
Purchase #4	$71.39	13.359%	$80.927	$80.93	$80.95	$80.90
Purchase #5	$147.31	13.152%	$166.6842	$166.68	$166.70	$166.70
Purchase #6	$58.84	6.119%	$62.4404	$62.44	$62.45	$62.40
Purchase #7	$172.92	10.410%	$190.921	$190.92	$190.90	$190.90
7 purchase totals =	$738.52		$819.9111	$819.91	$819.95	$819.80