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	$101.80	11.264%	$113.2668	$113.27	$113.25	$113.30
Purchase #2	$37.56	12.390%	$42.2137	$42.21	$42.20	$42.20
Purchase #3	$124.94	7.555%	$134.3792	$134.38	$134.40	$134.40
Purchase #4	$219.26	3.263%	$226.4145	$226.41	$226.40	$226.40
Purchase #5	$127.27	11.737%	$142.2077	$142.21	$142.20	$142.20
Purchase #6	$154.83	5.168%	$162.8316	$162.83	$162.85	$162.80
Purchase #7	$223.52	9.204%	$244.0928	$244.09	$244.10	$244.10
7 purchase totals =	$989.18		$1,065.4063	$1,065.40	$1,065.40	$1,065.40