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	$182.56	6.743%	$194.87	$194.87	$194.85	$194.90
Purchase #2	$7.50	10.620%	$8.2965	$8.30	$8.30	$8.30
Purchase #3	$59.33	12.312%	$66.6347	$66.63	$66.65	$66.60
Purchase #4	$85.64	4.523%	$89.5135	$89.51	$89.50	$89.50
Purchase #5	$192.88	6.411%	$205.2455	$205.25	$205.25	$205.20
Purchase #6	$166.83	13.478%	$189.3153	$189.32	$189.30	$189.30
Purchase #7	$97.50	5.556%	$102.9171	$102.92	$102.90	$102.90
7 purchase totals =	$792.24		$856.7926	$856.80	$856.75	$856.70