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	$219.98	4.194%	$229.206	$229.21	$229.20	$229.20
Purchase #2	$143.45	5.525%	$151.3756	$151.38	$151.40	$151.40
Purchase #3	$91.52	7.456%	$98.3437	$98.34	$98.35	$98.30
Purchase #4	$230.55	7.739%	$248.3923	$248.39	$248.40	$248.40
Purchase #5	$83.31	12.581%	$93.7912	$93.79	$93.80	$93.80
Purchase #6	$69.58	4.130%	$72.4537	$72.45	$72.45	$72.50
Purchase #7	$100.89	12.306%	$113.3055	$113.31	$113.30	$113.30
7 purchase totals =	$939.28		$1,006.8680	$1,006.87	$1,006.90	$1,006.90