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	$65.49	9.729%	$71.8615	$71.86	$71.85	$71.90
Purchase #2	$18.85	7.380%	$20.2411	$20.24	$20.25	$20.20
Purchase #3	$98.41	9.416%	$107.6763	$107.68	$107.70	$107.70
Purchase #4	$86.49	3.587%	$89.5924	$89.59	$89.60	$89.60
Purchase #5	$86.79	11.338%	$96.6303	$96.63	$96.65	$96.60
Purchase #6	$106.68	4.517%	$111.4987	$111.50	$111.50	$111.50
Purchase #7	$33.60	12.842%	$37.9149	$37.91	$37.90	$37.90
7 purchase totals =	$496.31		$535.4152	$535.41	$535.45	$535.40