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	$91.91	6.359%	$97.7546	$97.75	$97.75	$97.80
Purchase #2	$140.97	7.839%	$152.0206	$152.02	$152.00	$152.00
Purchase #3	$115.80	13.434%	$131.3566	$131.36	$131.35	$131.40
Purchase #4	$248.33	8.363%	$269.0978	$269.10	$269.10	$269.10
Purchase #5	$57.31	3.291%	$59.1961	$59.20	$59.20	$59.20
Purchase #6	$64.34	6.631%	$68.6064	$68.61	$68.60	$68.60
Purchase #7	$28.49	13.742%	$32.4051	$32.41	$32.40	$32.40
7 purchase totals =	$747.15		$810.4372	$810.45	$810.40	$810.50