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	$157.56	10.765%	$174.5213	$174.52	$174.50	$174.50
Purchase #2	$103.66	7.332%	$111.2604	$111.26	$111.25	$111.30
Purchase #3	$39.54	4.645%	$41.3766	$41.38	$41.40	$41.40
Purchase #4	$130.83	10.647%	$144.7595	$144.76	$144.75	$144.80
Purchase #5	$169.81	6.417%	$180.7067	$180.71	$180.70	$180.70
Purchase #6	$223.86	9.778%	$245.749	$245.75	$245.75	$245.70
Purchase #7	$59.91	6.411%	$63.7508	$63.75	$63.75	$63.80
7 purchase totals =	$885.17		$962.1243	$962.13	$962.10	$962.20