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	$152.40	6.622%	$162.4919	$162.49	$162.50	$162.50
Purchase #2	$144.30	8.612%	$156.7271	$156.73	$156.75	$156.70
Purchase #3	$47.77	5.364%	$50.3324	$50.33	$50.35	$50.30
Purchase #4	$190.39	7.200%	$204.0981	$204.10	$204.10	$204.10
Purchase #5	$185.99	6.797%	$198.6317	$198.63	$198.65	$198.60
Purchase #6	$89.67	11.494%	$99.9767	$99.98	$100.00	$100.00
Purchase #7	$133.32	9.218%	$145.6094	$145.61	$145.60	$145.60
7 purchase totals =	$943.84		$1,017.8673	$1,017.87	$1,017.95	$1,017.80