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	$56.26	6.442%	$59.8843	$59.88	$59.90	$59.90
Purchase #2	$165.27	13.566%	$187.6905	$187.69	$187.70	$187.70
Purchase #3	$234.76	11.653%	$262.1166	$262.12	$262.10	$262.10
Purchase #4	$6.53	6.244%	$6.9377	$6.94	$6.95	$6.90
Purchase #5	$135.52	4.742%	$141.9464	$141.95	$141.95	$141.90
Purchase #6	$99.55	12.623%	$112.1162	$112.12	$112.10	$112.10
Purchase #7	$230.62	4.453%	$240.8895	$240.89	$240.90	$240.90
7 purchase totals =	$928.51		$1,011.5812	$1,011.59	$1,011.60	$1,011.50