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	$183.79	9.672%	$201.5662	$201.57	$201.55	$201.60
Purchase #2	$91.44	6.674%	$97.5427	$97.54	$97.55	$97.50
Purchase #3	$247.59	6.726%	$264.2429	$264.24	$264.25	$264.20
Purchase #4	$250.74	12.606%	$282.3483	$282.35	$282.35	$282.30
Purchase #5	$162.87	10.107%	$179.3313	$179.33	$179.35	$179.30
Purchase #6	$77.98	5.212%	$82.0443	$82.04	$82.05	$82.00
Purchase #7	$82.45	8.861%	$89.7559	$89.76	$89.75	$89.80
7 purchase totals =	$1,096.86		$1,196.8316	$1,196.83	$1,196.85	$1,196.70