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	$191.69	6.516%	$204.1805	$204.18	$204.20	$204.20
Purchase #2	$136.71	10.680%	$151.3106	$151.31	$151.30	$151.30
Purchase #3	$129.64	3.589%	$134.2928	$134.29	$134.30	$134.30
Purchase #4	$49.87	11.346%	$55.5283	$55.53	$55.55	$55.50
Purchase #5	$78.56	9.496%	$86.0201	$86.02	$86.00	$86.00
Purchase #6	$168.26	11.663%	$187.8842	$187.88	$187.90	$187.90
Purchase #7	$162.27	3.517%	$167.977	$167.98	$168.00	$168.00
7 purchase totals =	$917.00		$987.1935	$987.19	$987.25	$987.20