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	$216.42	13.360%	$245.3337	$245.33	$245.35	$245.30
Purchase #2	$236.96	5.393%	$249.7393	$249.74	$249.75	$249.70
Purchase #3	$139.27	10.229%	$153.5159	$153.52	$153.50	$153.50
Purchase #4	$69.73	11.867%	$78.0049	$78.00	$78.00	$78.00
Purchase #5	$249.28	7.152%	$267.1085	$267.11	$267.10	$267.10
Purchase #6	$87.32	3.842%	$90.6748	$90.67	$90.65	$90.70
Purchase #7	$238.87	3.846%	$248.0569	$248.06	$248.05	$248.10
7 purchase totals =	$1,237.85		$1,332.4340	$1,332.43	$1,332.40	$1,332.40