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	$224.31	3.308%	$231.7302	$231.73	$231.75	$231.70
Purchase #2	$75.76	8.564%	$82.2481	$82.25	$82.25	$82.20
Purchase #3	$70.61	10.856%	$78.2754	$78.28	$78.30	$78.30
Purchase #4	$247.30	6.519%	$263.4215	$263.42	$263.40	$263.40
Purchase #5	$132.36	6.275%	$140.6656	$140.67	$140.65	$140.70
Purchase #6	$65.49	4.861%	$68.6735	$68.67	$68.65	$68.70
Purchase #7	$98.65	11.123%	$109.6228	$109.62	$109.60	$109.60
7 purchase totals =	$914.48		$974.6371	$974.64	$974.60	$974.60