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	$189.35	4.310%	$197.511	$197.51	$197.50	$197.50
Purchase #2	$223.75	10.683%	$247.6532	$247.65	$247.65	$247.70
Purchase #3	$114.66	10.781%	$127.0215	$127.02	$127.00	$127.00
Purchase #4	$145.77	13.306%	$165.1662	$165.17	$165.15	$165.20
Purchase #5	$73.96	11.417%	$82.404	$82.40	$82.40	$82.40
Purchase #6	$200.51	10.314%	$221.1906	$221.19	$221.20	$221.20
Purchase #7	$98.32	9.759%	$107.915	$107.92	$107.90	$107.90
7 purchase totals =	$1,046.32		$1,148.8615	$1,148.86	$1,148.80	$1,148.90