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	$58.91	6.538%	$62.7615	$62.76	$62.75	$62.80
Purchase #2	$206.56	10.403%	$228.0484	$228.05	$228.05	$228.00
Purchase #3	$227.81	13.286%	$258.0768	$258.08	$258.10	$258.10
Purchase #4	$182.69	6.540%	$194.6379	$194.64	$194.65	$194.60
Purchase #5	$203.72	3.260%	$210.3613	$210.36	$210.35	$210.40
Purchase #6	$86.53	11.412%	$96.4048	$96.40	$96.40	$96.40
Purchase #7	$89.59	12.223%	$100.5406	$100.54	$100.55	$100.50
7 purchase totals =	$1,055.81		$1,150.8313	$1,150.83	$1,150.85	$1,150.80