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	$16.87	13.865%	$19.209	$19.21	$19.20	$19.20
Purchase #2	$86.43	3.323%	$89.3021	$89.30	$89.30	$89.30
Purchase #3	$61.49	13.721%	$69.927	$69.93	$69.95	$69.90
Purchase #4	$153.25	9.139%	$167.2555	$167.26	$167.25	$167.30
Purchase #5	$123.68	5.607%	$130.6147	$130.61	$130.60	$130.60
Purchase #6	$40.36	12.357%	$45.3473	$45.35	$45.35	$45.30
Purchase #7	$170.71	6.250%	$181.3794	$181.38	$181.40	$181.40
7 purchase totals =	$652.79		$703.0350	$703.04	$703.05	$703.00