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	$130.43	3.333%	$134.7772	$134.78	$134.80	$134.80
Purchase #2	$96.52	11.213%	$107.3428	$107.34	$107.35	$107.30
Purchase #3	$99.46	5.426%	$104.8567	$104.86	$104.85	$104.90
Purchase #4	$89.36	13.583%	$101.4978	$101.50	$101.50	$101.50
Purchase #5	$205.74	13.470%	$233.4532	$233.45	$233.45	$233.50
Purchase #6	$145.80	3.432%	$150.8039	$150.80	$150.80	$150.80
Purchase #7	$56.45	6.249%	$59.9776	$59.98	$60.00	$60.00
7 purchase totals =	$823.76		$892.7092	$892.71	$892.75	$892.80