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	$108.25	8.123%	$117.0431	$117.04	$117.05	$117.00
Purchase #2	$17.64	9.596%	$19.3327	$19.33	$19.35	$19.30
Purchase #3	$214.38	9.548%	$234.849	$234.85	$234.85	$234.80
Purchase #4	$170.48	12.123%	$191.1473	$191.15	$191.15	$191.10
Purchase #5	$185.41	12.410%	$208.4194	$208.42	$208.40	$208.40
Purchase #6	$49.89	5.146%	$52.4573	$52.46	$52.45	$52.50
Purchase #7	$175.72	10.437%	$194.0599	$194.06	$194.05	$194.10
7 purchase totals =	$921.77		$1,017.3087	$1,017.31	$1,017.30	$1,017.20