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	$92.72	6.853%	$99.0741	$99.07	$99.05	$99.10
Purchase #2	$187.73	3.330%	$193.9814	$193.98	$194.00	$194.00
Purchase #3	$144.78	4.635%	$151.4906	$151.49	$151.50	$151.50
Purchase #4	$189.85	7.843%	$204.7399	$204.74	$204.75	$204.70
Purchase #5	$124.31	6.578%	$132.4871	$132.49	$132.50	$132.50
Purchase #6	$98.61	9.620%	$108.0963	$108.10	$108.10	$108.10
Purchase #7	$131.69	9.728%	$144.5008	$144.50	$144.50	$144.50
7 purchase totals =	$969.69		$1,034.3702	$1,034.37	$1,034.40	$1,034.40