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	$163.78	7.356%	$175.8277	$175.83	$175.85	$175.80
Purchase #2	$39.33	5.816%	$41.6174	$41.62	$41.60	$41.60
Purchase #3	$82.92	9.286%	$90.62	$90.62	$90.60	$90.60
Purchase #4	$85.86	9.293%	$93.839	$93.84	$93.85	$93.80
Purchase #5	$129.79	7.270%	$139.2257	$139.23	$139.25	$139.20
Purchase #6	$212.85	4.428%	$222.275	$222.28	$222.30	$222.30
Purchase #7	$186.59	5.457%	$196.7722	$196.77	$196.75	$196.80
7 purchase totals =	$901.12		$960.1770	$960.19	$960.20	$960.10