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	$140.90	8.745%	$153.2217	$153.22	$153.20	$153.20
Purchase #2	$88.61	8.720%	$96.3368	$96.34	$96.35	$96.30
Purchase #3	$42.46	7.851%	$45.7935	$45.79	$45.80	$45.80
Purchase #4	$20.88	4.759%	$21.8737	$21.87	$21.85	$21.90
Purchase #5	$75.71	6.599%	$80.7061	$80.71	$80.70	$80.70
Purchase #6	$104.52	4.152%	$108.8597	$108.86	$108.85	$108.90
Purchase #7	$103.70	13.846%	$118.0583	$118.06	$118.05	$118.10
7 purchase totals =	$576.78		$624.8498	$624.85	$624.80	$624.90