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	$232.95	11.227%	$259.1033	$259.10	$259.10	$259.10
Purchase #2	$184.48	4.241%	$192.3038	$192.30	$192.30	$192.30
Purchase #3	$166.61	11.182%	$185.2403	$185.24	$185.25	$185.20
Purchase #4	$78.59	13.661%	$89.3262	$89.33	$89.35	$89.30
Purchase #5	$75.72	9.828%	$83.1618	$83.16	$83.15	$83.20
Purchase #6	$198.27	4.553%	$207.2972	$207.30	$207.30	$207.30
Purchase #7	$97.97	8.115%	$105.9203	$105.92	$105.90	$105.90
7 purchase totals =	$1,034.59		$1,122.3529	$1,122.35	$1,122.35	$1,122.30