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	$149.63	4.487%	$156.3439	$156.34	$156.35	$156.30
Purchase #2	$238.71	13.360%	$270.6017	$270.60	$270.60	$270.60
Purchase #3	$158.92	12.322%	$178.5021	$178.50	$178.50	$178.50
Purchase #4	$73.67	6.141%	$78.1941	$78.19	$78.20	$78.20
Purchase #5	$64.36	12.309%	$72.2821	$72.28	$72.30	$72.30
Purchase #6	$226.27	5.400%	$238.4886	$238.49	$238.50	$238.50
Purchase #7	$96.65	8.148%	$104.525	$104.53	$104.55	$104.50
7 purchase totals =	$1,008.21		$1,098.9375	$1,098.93	$1,099.00	$1,098.90