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	$82.71	11.825%	$92.4905	$92.49	$92.50	$92.50
Purchase #2	$31.30	6.594%	$33.3639	$33.36	$33.35	$33.40
Purchase #3	$43.97	10.503%	$48.5882	$48.59	$48.60	$48.60
Purchase #4	$245.28	7.494%	$263.6613	$263.66	$263.65	$263.70
Purchase #5	$26.64	3.185%	$27.4885	$27.49	$27.50	$27.50
Purchase #6	$89.27	12.860%	$100.7501	$100.75	$100.75	$100.80
Purchase #7	$150.86	12.391%	$169.5531	$169.55	$169.55	$169.60
7 purchase totals =	$670.03		$735.8956	$735.89	$735.90	$736.10