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	$121.99	4.637%	$127.6467	$127.65	$127.65	$127.60
Purchase #2	$75.25	4.534%	$78.6618	$78.66	$78.65	$78.70
Purchase #3	$152.77	6.633%	$162.9032	$162.90	$162.90	$162.90
Purchase #4	$187.81	3.152%	$193.7298	$193.73	$193.75	$193.70
Purchase #5	$19.57	5.503%	$20.6469	$20.65	$20.65	$20.60
Purchase #6	$197.83	9.112%	$215.8563	$215.86	$215.85	$215.90
Purchase #7	$161.50	4.546%	$168.8418	$168.84	$168.85	$168.80
7 purchase totals =	$916.72		$968.2865	$968.29	$968.30	$968.20