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	$80.25	11.538%	$89.5092	$89.51	$89.50	$89.50
Purchase #2	$72.35	3.714%	$75.0371	$75.04	$75.05	$75.00
Purchase #3	$210.64	5.778%	$222.8108	$222.81	$222.80	$222.80
Purchase #4	$67.97	13.638%	$77.2397	$77.24	$77.25	$77.20
Purchase #5	$133.33	13.614%	$151.4815	$151.48	$151.50	$151.50
Purchase #6	$245.76	4.823%	$257.613	$257.61	$257.60	$257.60
Purchase #7	$64.90	5.305%	$68.3429	$68.34	$68.35	$68.30
7 purchase totals =	$875.20		$942.0342	$942.03	$942.05	$941.90