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	$248.71	5.390%	$262.1155	$262.12	$262.10	$262.10
Purchase #2	$160.45	13.738%	$182.4926	$182.49	$182.50	$182.50
Purchase #3	$243.89	8.426%	$264.4402	$264.44	$264.45	$264.40
Purchase #4	$135.36	4.202%	$141.0478	$141.05	$141.05	$141.00
Purchase #5	$117.27	5.423%	$123.6296	$123.63	$123.65	$123.60
Purchase #6	$40.52	11.735%	$45.275	$45.28	$45.30	$45.30
Purchase #7	$99.53	10.559%	$110.0394	$110.04	$110.05	$110.00
7 purchase totals =	$1,045.73		$1,129.0401	$1,129.05	$1,129.10	$1,128.90