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	$236.33	12.608%	$266.1265	$266.13	$266.15	$266.10
Purchase #2	$10.38	7.618%	$11.1707	$11.17	$11.15	$11.20
Purchase #3	$74.66	10.839%	$82.7524	$82.75	$82.75	$82.80
Purchase #4	$186.38	5.505%	$196.6402	$196.64	$196.65	$196.60
Purchase #5	$241.41	3.608%	$250.1201	$250.12	$250.10	$250.10
Purchase #6	$16.88	7.639%	$18.1695	$18.17	$18.15	$18.20
Purchase #7	$55.49	6.452%	$59.0702	$59.07	$59.05	$59.10
7 purchase totals =	$821.53		$884.0496	$884.05	$884.00	$884.10