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	$35.37	8.257%	$38.2905	$38.29	$38.30	$38.30
Purchase #2	$62.85	6.714%	$67.0697	$67.07	$67.05	$67.10
Purchase #3	$69.36	13.627%	$78.8117	$78.81	$78.80	$78.80
Purchase #4	$150.87	3.482%	$156.1233	$156.12	$156.10	$156.10
Purchase #5	$14.63	10.613%	$16.1827	$16.18	$16.20	$16.20
Purchase #6	$6.86	10.210%	$7.5604	$7.56	$7.55	$7.60
Purchase #7	$30.33	10.660%	$33.5632	$33.56	$33.55	$33.60
7 purchase totals =	$370.27		$397.6015	$397.59	$397.55	$397.70