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	$111.41	4.437%	$116.3533	$116.35	$116.35	$116.40
Purchase #2	$78.64	4.347%	$82.0585	$82.06	$82.05	$82.10
Purchase #3	$6.53	11.289%	$7.2672	$7.27	$7.25	$7.30
Purchase #4	$194.53	12.793%	$219.4162	$219.42	$219.40	$219.40
Purchase #5	$53.55	8.253%	$57.9695	$57.97	$57.95	$58.00
Purchase #6	$59.31	5.569%	$62.613	$62.61	$62.60	$62.60
Purchase #7	$80.63	3.337%	$83.3206	$83.32	$83.30	$83.30
7 purchase totals =	$584.60		$628.9983	$629.00	$628.90	$629.10