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	$186.58	3.203%	$192.5562	$192.56	$192.55	$192.60
Purchase #2	$222.86	8.380%	$241.5357	$241.54	$241.55	$241.50
Purchase #3	$204.86	5.631%	$216.3957	$216.40	$216.40	$216.40
Purchase #4	$85.70	8.796%	$93.2382	$93.24	$93.25	$93.20
Purchase #5	$89.33	10.587%	$98.7874	$98.79	$98.80	$98.80
Purchase #6	$180.82	8.453%	$196.1047	$196.10	$196.10	$196.10
Purchase #7	$105.31	11.109%	$117.0089	$117.01	$117.00	$117.00
7 purchase totals =	$1,075.46		$1,155.6268	$1,155.64	$1,155.65	$1,155.60