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	$241.97	5.620%	$255.5687	$255.57	$255.55	$255.60
Purchase #2	$31.41	11.729%	$35.0941	$35.09	$35.10	$35.10
Purchase #3	$80.32	11.637%	$89.6668	$89.67	$89.65	$89.70
Purchase #4	$95.69	6.353%	$101.7692	$101.77	$101.75	$101.80
Purchase #5	$161.31	6.633%	$172.0097	$172.01	$172.00	$172.00
Purchase #6	$8.39	5.815%	$8.8779	$8.88	$8.90	$8.90
Purchase #7	$197.30	6.645%	$210.4106	$210.41	$210.40	$210.40
7 purchase totals =	$816.39		$873.3970	$873.40	$873.35	$873.50