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	$188.64	4.270%	$196.6949	$196.69	$196.70	$196.70
Purchase #2	$144.62	11.467%	$161.2036	$161.20	$161.20	$161.20
Purchase #3	$142.43	7.284%	$152.8046	$152.80	$152.80	$152.80
Purchase #4	$56.64	4.198%	$59.0177	$59.02	$59.00	$59.00
Purchase #5	$195.95	9.861%	$215.2726	$215.27	$215.25	$215.30
Purchase #6	$100.96	8.866%	$109.9111	$109.91	$109.90	$109.90
Purchase #7	$65.51	7.307%	$70.2968	$70.30	$70.30	$70.30
7 purchase totals =	$894.75		$965.2013	$965.19	$965.15	$965.20