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	$120.36	5.767%	$127.3012	$127.30	$127.30	$127.30
Purchase #2	$68.71	4.436%	$71.758	$71.76	$71.75	$71.80
Purchase #3	$163.69	10.285%	$180.5255	$180.53	$180.55	$180.50
Purchase #4	$124.71	13.612%	$141.6855	$141.69	$141.70	$141.70
Purchase #5	$222.90	6.325%	$236.9984	$237.00	$237.00	$237.00
Purchase #6	$69.28	7.732%	$74.6367	$74.64	$74.65	$74.60
Purchase #7	$167.40	11.381%	$186.4518	$186.45	$186.45	$186.50
7 purchase totals =	$937.05		$1,019.3571	$1,019.37	$1,019.40	$1,019.40