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	$63.80	5.512%	$67.3167	$67.32	$67.30	$67.30
Purchase #2	$59.89	10.717%	$66.3084	$66.31	$66.30	$66.30
Purchase #3	$238.66	12.355%	$268.1464	$268.15	$268.15	$268.10
Purchase #4	$144.39	13.794%	$164.3072	$164.31	$164.30	$164.30
Purchase #5	$134.32	10.166%	$147.975	$147.98	$148.00	$148.00
Purchase #6	$48.72	10.678%	$53.9223	$53.92	$53.90	$53.90
Purchase #7	$246.63	13.824%	$280.7241	$280.72	$280.70	$280.70
7 purchase totals =	$936.41		$1,048.7001	$1,048.71	$1,048.65	$1,048.60