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	$72.73	5.452%	$76.6952	$76.70	$76.70	$76.70
Purchase #2	$225.42	4.654%	$235.911	$235.91	$235.90	$235.90
Purchase #3	$159.74	12.254%	$179.3145	$179.31	$179.30	$179.30
Purchase #4	$94.53	6.651%	$100.8172	$100.82	$100.80	$100.80
Purchase #5	$221.47	9.470%	$242.4432	$242.44	$242.45	$242.40
Purchase #6	$216.93	11.510%	$241.8986	$241.90	$241.90	$241.90
Purchase #7	$7.63	8.442%	$8.2741	$8.27	$8.25	$8.30
7 purchase totals =	$998.45		$1,085.3538	$1,085.35	$1,085.30	$1,085.30