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	$33.53	6.134%	$35.5867	$35.59	$35.60	$35.60
Purchase #2	$152.46	10.593%	$168.6101	$168.61	$168.60	$168.60
Purchase #3	$221.49	3.534%	$229.3175	$229.32	$229.30	$229.30
Purchase #4	$250.77	11.152%	$278.7359	$278.74	$278.75	$278.70
Purchase #5	$166.61	3.421%	$172.3097	$172.31	$172.30	$172.30
Purchase #6	$233.75	5.199%	$245.9027	$245.90	$245.90	$245.90
Purchase #7	$151.67	7.859%	$163.5897	$163.59	$163.60	$163.60
7 purchase totals =	$1,210.28		$1,294.0523	$1,294.06	$1,294.05	$1,294.00