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	$29.56	11.822%	$33.0546	$33.05	$33.05	$33.10
Purchase #2	$121.94	4.470%	$127.3907	$127.39	$127.40	$127.40
Purchase #3	$119.57	9.464%	$130.8861	$130.89	$130.90	$130.90
Purchase #4	$22.70	5.478%	$23.9435	$23.94	$23.95	$23.90
Purchase #5	$29.27	6.240%	$31.0964	$31.10	$31.10	$31.10
Purchase #6	$37.82	12.270%	$42.4605	$42.46	$42.45	$42.50
Purchase #7	$14.41	12.687%	$16.2382	$16.24	$16.25	$16.20
7 purchase totals =	$375.27		$405.0700	$405.07	$405.10	$405.10