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	$61.34	13.300%	$69.4982	$69.50	$69.50	$69.50
Purchase #2	$106.77	4.212%	$111.2672	$111.27	$111.25	$111.30
Purchase #3	$179.79	13.531%	$204.1174	$204.12	$204.10	$204.10
Purchase #4	$162.61	7.811%	$175.3115	$175.31	$175.30	$175.30
Purchase #5	$108.97	10.619%	$120.5415	$120.54	$120.55	$120.50
Purchase #6	$151.36	7.209%	$162.2715	$162.27	$162.25	$162.30
Purchase #7	$233.45	13.477%	$264.9121	$264.91	$264.90	$264.90
7 purchase totals =	$1,004.29		$1,107.9194	$1,107.92	$1,107.85	$1,107.90