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	$196.81	9.664%	$215.8297	$215.83	$215.85	$215.80
Purchase #2	$108.43	7.799%	$116.8865	$116.89	$116.90	$116.90
Purchase #3	$79.87	12.222%	$89.6317	$89.63	$89.65	$89.60
Purchase #4	$176.76	7.676%	$190.3281	$190.33	$190.35	$190.30
Purchase #5	$106.62	9.125%	$116.3491	$116.35	$116.35	$116.30
Purchase #6	$110.26	7.630%	$118.6728	$118.67	$118.65	$118.70
Purchase #7	$181.98	6.870%	$194.482	$194.48	$194.50	$194.50
7 purchase totals =	$960.73		$1,042.1799	$1,042.18	$1,042.25	$1,042.10