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	$57.76	7.192%	$61.9141	$61.91	$61.90	$61.90
Purchase #2	$233.46	13.532%	$265.0518	$265.05	$265.05	$265.10
Purchase #3	$70.92	10.724%	$78.5255	$78.53	$78.55	$78.50
Purchase #4	$86.48	12.183%	$97.0159	$97.02	$97.00	$97.00
Purchase #5	$209.73	9.479%	$229.6103	$229.61	$229.60	$229.60
Purchase #6	$210.69	12.823%	$237.7068	$237.71	$237.70	$237.70
Purchase #7	$97.89	11.389%	$109.0387	$109.04	$109.05	$109.00
7 purchase totals =	$966.93		$1,078.8631	$1,078.87	$1,078.85	$1,078.80