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	$93.81	5.364%	$98.842	$98.84	$98.85	$98.80
Purchase #2	$48.87	12.114%	$54.7901	$54.79	$54.80	$54.80
Purchase #3	$155.37	7.389%	$166.8503	$166.85	$166.85	$166.90
Purchase #4	$215.86	11.608%	$240.917	$240.92	$240.90	$240.90
Purchase #5	$80.69	11.739%	$90.1622	$90.16	$90.15	$90.20
Purchase #6	$149.92	12.115%	$168.0828	$168.08	$168.10	$168.10
Purchase #7	$219.83	10.606%	$243.1452	$243.15	$243.15	$243.10
7 purchase totals =	$964.35		$1,062.7896	$1,062.79	$1,062.80	$1,062.80