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	$210.90	11.572%	$235.3053	$235.31	$235.30	$235.30
Purchase #2	$221.48	3.755%	$229.7966	$229.80	$229.80	$229.80
Purchase #3	$50.93	5.258%	$53.6079	$53.61	$53.60	$53.60
Purchase #4	$140.83	8.355%	$152.5963	$152.60	$152.60	$152.60
Purchase #5	$110.93	11.302%	$123.4673	$123.47	$123.45	$123.50
Purchase #6	$203.60	6.396%	$216.6223	$216.62	$216.60	$216.60
Purchase #7	$158.98	6.194%	$168.8272	$168.83	$168.85	$168.80
7 purchase totals =	$1,097.65		$1,180.2229	$1,180.24	$1,180.20	$1,180.20