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	$105.25	7.709%	$113.3637	$113.36	$113.35	$113.40
Purchase #2	$135.74	5.270%	$142.8935	$142.89	$142.90	$142.90
Purchase #3	$31.86	11.127%	$35.4051	$35.41	$35.40	$35.40
Purchase #4	$161.39	13.126%	$182.5741	$182.57	$182.55	$182.60
Purchase #5	$159.29	8.686%	$173.1259	$173.13	$173.15	$173.10
Purchase #6	$247.27	6.211%	$262.6279	$262.63	$262.65	$262.60
Purchase #7	$47.97	11.471%	$53.4726	$53.47	$53.45	$53.50
7 purchase totals =	$888.77		$963.4628	$963.46	$963.45	$963.50