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	$169.84	10.837%	$188.2456	$188.25	$188.25	$188.20
Purchase #2	$245.68	10.154%	$270.6263	$270.63	$270.65	$270.60
Purchase #3	$68.51	9.697%	$75.1534	$75.15	$75.15	$75.20
Purchase #4	$84.45	7.681%	$90.9366	$90.94	$90.95	$90.90
Purchase #5	$250.71	7.109%	$268.533	$268.53	$268.55	$268.50
Purchase #6	$245.89	3.660%	$254.8896	$254.89	$254.90	$254.90
Purchase #7	$71.72	9.109%	$78.253	$78.25	$78.25	$78.30
7 purchase totals =	$1,136.80		$1,226.6375	$1,226.64	$1,226.70	$1,226.60