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	$105.46	4.144%	$109.8303	$109.83	$109.85	$109.80
Purchase #2	$195.30	4.374%	$203.8424	$203.84	$203.85	$203.80
Purchase #3	$81.43	5.573%	$85.9681	$85.97	$85.95	$86.00
Purchase #4	$140.28	11.610%	$156.5665	$156.57	$156.55	$156.60
Purchase #5	$52.67	10.441%	$58.1693	$58.17	$58.15	$58.20
Purchase #6	$89.46	13.845%	$101.8457	$101.85	$101.85	$101.80
Purchase #7	$154.50	6.412%	$164.4065	$164.41	$164.40	$164.40
7 purchase totals =	$819.10		$880.6288	$880.64	$880.60	$880.60