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	$83.73	5.129%	$88.0245	$88.02	$88.00	$88.00
Purchase #2	$89.71	10.629%	$99.2453	$99.25	$99.25	$99.20
Purchase #3	$204.72	13.549%	$232.4575	$232.46	$232.45	$232.50
Purchase #4	$113.76	7.759%	$122.5866	$122.59	$122.60	$122.60
Purchase #5	$91.73	11.820%	$102.5725	$102.57	$102.55	$102.60
Purchase #6	$156.45	11.799%	$174.9095	$174.91	$174.90	$174.90
Purchase #7	$165.37	9.669%	$181.3596	$181.36	$181.35	$181.40
7 purchase totals =	$905.47		$1,001.1555	$1,001.16	$1,001.10	$1,001.20