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	$67.39	10.780%	$74.6546	$74.65	$74.65	$74.70
Purchase #2	$39.78	6.745%	$42.4632	$42.46	$42.45	$42.50
Purchase #3	$120.52	5.802%	$127.5126	$127.51	$127.50	$127.50
Purchase #4	$76.77	8.145%	$83.0229	$83.02	$83.00	$83.00
Purchase #5	$113.92	13.489%	$129.2867	$129.29	$129.30	$129.30
Purchase #6	$28.99	12.450%	$32.5993	$32.60	$32.60	$32.60
Purchase #7	$174.66	13.806%	$198.7736	$198.77	$198.75	$198.80
7 purchase totals =	$622.03		$688.3129	$688.30	$688.25	$688.40