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	$243.55	8.510%	$264.2761	$264.28	$264.30	$264.30
Purchase #2	$53.31	4.175%	$55.5357	$55.54	$55.55	$55.50
Purchase #3	$32.73	12.174%	$36.7146	$36.71	$36.70	$36.70
Purchase #4	$48.56	3.161%	$50.095	$50.10	$50.10	$50.10
Purchase #5	$32.39	10.161%	$35.6811	$35.68	$35.70	$35.70
Purchase #6	$70.27	11.334%	$78.2344	$78.23	$78.25	$78.20
Purchase #7	$179.36	4.305%	$187.0814	$187.08	$187.10	$187.10
7 purchase totals =	$660.17		$707.6183	$707.62	$707.70	$707.60