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	$195.47	12.391%	$219.6907	$219.69	$219.70	$219.70
Purchase #2	$98.37	13.312%	$111.465	$111.47	$111.45	$111.50
Purchase #3	$92.25	9.749%	$101.2435	$101.24	$101.25	$101.20
Purchase #4	$17.62	4.822%	$18.4696	$18.47	$18.45	$18.50
Purchase #5	$90.66	6.241%	$96.3181	$96.32	$96.30	$96.30
Purchase #6	$103.72	4.839%	$108.739	$108.74	$108.75	$108.70
Purchase #7	$154.25	5.331%	$162.4731	$162.47	$162.45	$162.50
7 purchase totals =	$752.34		$818.3990	$818.40	$818.35	$818.40