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	$177.50	11.735%	$198.3296	$198.33	$198.35	$198.30
Purchase #2	$53.29	11.498%	$59.4173	$59.42	$59.40	$59.40
Purchase #3	$75.32	12.798%	$84.9595	$84.96	$84.95	$85.00
Purchase #4	$135.51	7.787%	$146.0622	$146.06	$146.05	$146.10
Purchase #5	$115.79	3.240%	$119.5416	$119.54	$119.55	$119.50
Purchase #6	$46.92	8.144%	$50.7412	$50.74	$50.75	$50.70
Purchase #7	$83.89	8.125%	$90.7061	$90.71	$90.70	$90.70
7 purchase totals =	$688.22		$749.7575	$749.76	$749.75	$749.70