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	$102.67	3.192%	$105.9472	$105.95	$105.95	$105.90
Purchase #2	$78.48	12.838%	$88.5553	$88.56	$88.55	$88.60
Purchase #3	$186.84	3.717%	$193.7848	$193.78	$193.80	$193.80
Purchase #4	$154.68	11.270%	$172.1124	$172.11	$172.10	$172.10
Purchase #5	$102.41	8.618%	$111.2357	$111.24	$111.25	$111.20
Purchase #6	$165.31	12.372%	$185.7622	$185.76	$185.75	$185.80
Purchase #7	$51.84	5.266%	$54.5699	$54.57	$54.55	$54.60
7 purchase totals =	$842.23		$911.9675	$911.97	$911.95	$912.00