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	$75.52	7.345%	$81.0669	$81.07	$81.05	$81.10
Purchase #2	$78.85	9.496%	$86.3376	$86.34	$86.35	$86.30
Purchase #3	$132.56	7.454%	$142.441	$142.44	$142.45	$142.40
Purchase #4	$9.94	5.343%	$10.4711	$10.47	$10.45	$10.50
Purchase #5	$151.27	4.486%	$158.056	$158.06	$158.05	$158.10
Purchase #6	$198.40	8.643%	$215.5477	$215.55	$215.55	$215.50
Purchase #7	$233.37	9.861%	$256.3826	$256.38	$256.40	$256.40
7 purchase totals =	$879.91		$950.3029	$950.31	$950.30	$950.30