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	$64.66	12.330%	$72.6326	$72.63	$72.65	$72.60
Purchase #2	$31.79	5.728%	$33.6109	$33.61	$33.60	$33.60
Purchase #3	$216.56	5.495%	$228.46	$228.46	$228.45	$228.50
Purchase #4	$79.61	8.345%	$86.2535	$86.25	$86.25	$86.30
Purchase #5	$39.91	5.443%	$42.0823	$42.08	$42.10	$42.10
Purchase #6	$208.49	12.854%	$235.2893	$235.29	$235.30	$235.30
Purchase #7	$88.70	5.509%	$93.5865	$93.59	$93.60	$93.60
7 purchase totals =	$729.72		$791.9151	$791.91	$791.95	$792.00