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	$54.82	5.667%	$57.9266	$57.93	$57.95	$57.90
Purchase #2	$6.93	5.441%	$7.3071	$7.31	$7.30	$7.30
Purchase #3	$90.26	9.694%	$99.0098	$99.01	$99.00	$99.00
Purchase #4	$19.84	5.467%	$20.9247	$20.92	$20.90	$20.90
Purchase #5	$221.73	6.496%	$236.1336	$236.13	$236.15	$236.10
Purchase #6	$52.76	13.690%	$59.9828	$59.98	$60.00	$60.00
Purchase #7	$216.92	11.159%	$241.1261	$241.13	$241.15	$241.10
7 purchase totals =	$663.26		$722.4107	$722.41	$722.45	$722.30