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	$126.36	12.711%	$142.4216	$142.42	$142.40	$142.40
Purchase #2	$114.53	9.582%	$125.5043	$125.50	$125.50	$125.50
Purchase #3	$237.32	11.503%	$264.6189	$264.62	$264.60	$264.60
Purchase #4	$95.89	3.802%	$99.5357	$99.54	$99.55	$99.50
Purchase #5	$40.43	3.570%	$41.8734	$41.87	$41.85	$41.90
Purchase #6	$155.91	9.743%	$171.1003	$171.10	$171.10	$171.10
Purchase #7	$157.82	10.732%	$174.7572	$174.76	$174.75	$174.80
7 purchase totals =	$928.26		$1,019.8114	$1,019.81	$1,019.75	$1,019.80