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	$187.72	4.496%	$196.1599	$196.16	$196.15	$196.20
Purchase #2	$15.76	13.649%	$17.9111	$17.91	$17.90	$17.90
Purchase #3	$39.91	5.822%	$42.2336	$42.23	$42.25	$42.20
Purchase #4	$96.64	7.711%	$104.0919	$104.09	$104.10	$104.10
Purchase #5	$38.34	7.312%	$41.1434	$41.14	$41.15	$41.10
Purchase #6	$5.46	11.537%	$6.0899	$6.09	$6.10	$6.10
Purchase #7	$26.89	13.819%	$30.6059	$30.61	$30.60	$30.60
7 purchase totals =	$410.72		$438.2357	$438.23	$438.25	$438.20