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	$69.43	4.276%	$72.3988	$72.40	$72.40	$72.40
Purchase #2	$52.87	8.321%	$57.2693	$57.27	$57.25	$57.30
Purchase #3	$12.81	12.586%	$14.4223	$14.42	$14.40	$14.40
Purchase #4	$217.78	3.282%	$224.9275	$224.93	$224.95	$224.90
Purchase #5	$175.66	13.372%	$199.1493	$199.15	$199.15	$199.10
Purchase #6	$188.58	6.172%	$200.2192	$200.22	$200.20	$200.20
Purchase #7	$67.73	12.460%	$76.1692	$76.17	$76.15	$76.20
7 purchase totals =	$784.86		$844.5556	$844.56	$844.50	$844.50