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	$158.62	5.443%	$167.2537	$167.25	$167.25	$167.30
Purchase #2	$24.89	9.666%	$27.2959	$27.30	$27.30	$27.30
Purchase #3	$189.91	3.174%	$195.9377	$195.94	$195.95	$195.90
Purchase #4	$82.37	8.442%	$89.3237	$89.32	$89.30	$89.30
Purchase #5	$10.42	10.798%	$11.5452	$11.55	$11.55	$11.50
Purchase #6	$86.87	10.515%	$96.0044	$96.00	$96.00	$96.00
Purchase #7	$219.80	5.192%	$231.212	$231.21	$231.20	$231.20
7 purchase totals =	$772.88		$818.5726	$818.57	$818.55	$818.50