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	$71.54	10.308%	$78.9143	$78.91	$78.90	$78.90
Purchase #2	$105.90	4.842%	$111.0277	$111.03	$111.05	$111.00
Purchase #3	$101.94	10.498%	$112.6417	$112.64	$112.65	$112.60
Purchase #4	$168.79	13.121%	$190.9369	$190.94	$190.95	$190.90
Purchase #5	$155.76	10.836%	$172.6382	$172.64	$172.65	$172.60
Purchase #6	$224.76	13.391%	$254.8576	$254.86	$254.85	$254.90
Purchase #7	$113.80	8.470%	$123.4389	$123.44	$123.45	$123.40
7 purchase totals =	$942.49		$1,044.4553	$1,044.46	$1,044.50	$1,044.30