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	$19.65	3.111%	$20.2613	$20.26	$20.25	$20.30
Purchase #2	$73.74	10.212%	$81.2703	$81.27	$81.25	$81.30
Purchase #3	$136.73	5.872%	$144.7588	$144.76	$144.75	$144.80
Purchase #4	$12.39	10.716%	$13.7177	$13.72	$13.70	$13.70
Purchase #5	$156.41	4.149%	$162.8995	$162.90	$162.90	$162.90
Purchase #6	$219.91	10.386%	$242.7499	$242.75	$242.75	$242.70
Purchase #7	$110.30	12.285%	$123.8504	$123.85	$123.85	$123.90
7 purchase totals =	$729.13		$789.5079	$789.51	$789.45	$789.60