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	$174.34	12.716%	$196.5091	$196.51	$196.50	$196.50
Purchase #2	$39.89	10.178%	$43.95	$43.95	$43.95	$44.00
Purchase #3	$121.32	5.337%	$127.7948	$127.79	$127.80	$127.80
Purchase #4	$67.41	6.767%	$71.9716	$71.97	$71.95	$72.00
Purchase #5	$170.28	9.739%	$186.8636	$186.86	$186.85	$186.90
Purchase #6	$89.68	12.533%	$100.9196	$100.92	$100.90	$100.90
Purchase #7	$68.65	12.459%	$77.2031	$77.20	$77.20	$77.20
7 purchase totals =	$731.57		$805.2118	$805.20	$805.15	$805.30