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	$125.85	4.745%	$131.8216	$131.82	$131.80	$131.80
Purchase #2	$219.50	3.780%	$227.7971	$227.80	$227.80	$227.80
Purchase #3	$76.26	9.323%	$83.3697	$83.37	$83.35	$83.40
Purchase #4	$215.55	13.103%	$243.7935	$243.79	$243.80	$243.80
Purchase #5	$12.91	9.665%	$14.1578	$14.16	$14.15	$14.20
Purchase #6	$57.32	12.816%	$64.6661	$64.67	$64.65	$64.70
Purchase #7	$119.86	6.300%	$127.4112	$127.41	$127.40	$127.40
7 purchase totals =	$827.25		$893.0170	$893.02	$892.95	$893.10