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	$199.32	5.449%	$210.1809	$210.18	$210.20	$210.20
Purchase #2	$83.96	6.567%	$89.4737	$89.47	$89.45	$89.50
Purchase #3	$38.77	9.310%	$42.3795	$42.38	$42.40	$42.40
Purchase #4	$115.63	4.137%	$120.4136	$120.41	$120.40	$120.40
Purchase #5	$170.51	9.327%	$186.4135	$186.41	$186.40	$186.40
Purchase #6	$130.58	4.834%	$136.8922	$136.89	$136.90	$136.90
Purchase #7	$219.37	5.353%	$231.1129	$231.11	$231.10	$231.10
7 purchase totals =	$958.14		$1,016.8663	$1,016.85	$1,016.85	$1,016.90