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	$66.61	5.207%	$70.0784	$70.08	$70.10	$70.10
Purchase #2	$185.33	5.555%	$195.6251	$195.63	$195.65	$195.60
Purchase #3	$45.68	6.369%	$48.5894	$48.59	$48.60	$48.60
Purchase #4	$127.63	12.713%	$143.8556	$143.86	$143.85	$143.90
Purchase #5	$213.35	4.119%	$222.1379	$222.14	$222.15	$222.10
Purchase #6	$92.34	7.108%	$98.9035	$98.90	$98.90	$98.90
Purchase #7	$110.67	11.231%	$123.0993	$123.10	$123.10	$123.10
7 purchase totals =	$841.61		$902.2892	$902.30	$902.35	$902.30