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	$186.27	12.802%	$210.1163	$210.12	$210.10	$210.10
Purchase #2	$32.82	3.581%	$33.9953	$34.00	$34.00	$34.00
Purchase #3	$94.29	9.845%	$103.5729	$103.57	$103.55	$103.60
Purchase #4	$146.53	3.852%	$152.1743	$152.17	$152.15	$152.20
Purchase #5	$31.75	4.264%	$33.1038	$33.10	$33.10	$33.10
Purchase #6	$76.48	3.424%	$79.0987	$79.10	$79.10	$79.10
Purchase #7	$184.43	3.201%	$190.3336	$190.33	$190.35	$190.30
7 purchase totals =	$752.57		$802.3949	$802.39	$802.35	$802.40