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	$73.47	5.606%	$77.5887	$77.59	$77.60	$77.60
Purchase #2	$141.35	4.295%	$147.421	$147.42	$147.40	$147.40
Purchase #3	$172.99	9.825%	$189.9863	$189.99	$190.00	$190.00
Purchase #4	$184.79	3.835%	$191.8767	$191.88	$191.90	$191.90
Purchase #5	$108.84	3.199%	$112.3218	$112.32	$112.30	$112.30
Purchase #6	$123.89	5.714%	$130.9691	$130.97	$130.95	$131.00
Purchase #7	$187.87	4.579%	$196.4726	$196.47	$196.45	$196.50
7 purchase totals =	$993.20		$1,046.6362	$1,046.64	$1,046.60	$1,046.70