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	$185.69	5.793%	$196.447	$196.45	$196.45	$196.40
Purchase #2	$170.82	5.481%	$180.1826	$180.18	$180.20	$180.20
Purchase #3	$114.76	6.742%	$122.4971	$122.50	$122.50	$122.50
Purchase #4	$86.43	11.208%	$96.1171	$96.12	$96.10	$96.10
Purchase #5	$56.58	9.388%	$61.8917	$61.89	$61.90	$61.90
Purchase #6	$83.47	7.378%	$89.6284	$89.63	$89.65	$89.60
Purchase #7	$129.53	9.215%	$141.4662	$141.47	$141.45	$141.50
7 purchase totals =	$827.28		$888.2301	$888.24	$888.25	$888.20