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	$172.46	7.614%	$185.5911	$185.59	$185.60	$185.60
Purchase #2	$219.48	12.812%	$247.5998	$247.60	$247.60	$247.60
Purchase #3	$134.38	4.381%	$140.2672	$140.27	$140.25	$140.30
Purchase #4	$96.77	4.541%	$101.1643	$101.16	$101.15	$101.20
Purchase #5	$27.77	4.658%	$29.0635	$29.06	$29.05	$29.10
Purchase #6	$93.57	11.799%	$104.6103	$104.61	$104.60	$104.60
Purchase #7	$89.44	7.865%	$96.4745	$96.47	$96.45	$96.50
7 purchase totals =	$833.87		$904.7707	$904.76	$904.70	$904.90