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	$47.33	12.572%	$53.2803	$53.28	$53.30	$53.30
Purchase #2	$158.31	10.764%	$175.3505	$175.35	$175.35	$175.40
Purchase #3	$137.41	9.521%	$150.4928	$150.49	$150.50	$150.50
Purchase #4	$203.86	11.839%	$227.995	$228.00	$228.00	$228.00
Purchase #5	$176.30	8.366%	$191.0493	$191.05	$191.05	$191.00
Purchase #6	$41.49	9.424%	$45.4	$45.40	$45.40	$45.40
Purchase #7	$60.80	7.639%	$65.4445	$65.44	$65.45	$65.40
7 purchase totals =	$825.50		$909.0124	$909.01	$909.05	$909.00