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	$173.38	7.641%	$186.628	$186.63	$186.65	$186.60
Purchase #2	$50.89	7.765%	$54.8416	$54.84	$54.85	$54.80
Purchase #3	$93.59	10.394%	$103.3177	$103.32	$103.30	$103.30
Purchase #4	$214.98	10.191%	$236.8886	$236.89	$236.90	$236.90
Purchase #5	$148.43	3.322%	$153.3608	$153.36	$153.35	$153.40
Purchase #6	$228.71	4.388%	$238.7458	$238.75	$238.75	$238.70
Purchase #7	$188.67	12.214%	$211.7142	$211.71	$211.70	$211.70
7 purchase totals =	$1,098.65		$1,185.4967	$1,185.50	$1,185.50	$1,185.40