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	$105.26	8.549%	$114.2587	$114.26	$114.25	$114.30
Purchase #2	$237.72	4.502%	$248.4222	$248.42	$248.40	$248.40
Purchase #3	$179.74	3.122%	$185.3515	$185.35	$185.35	$185.40
Purchase #4	$105.75	3.641%	$109.6004	$109.60	$109.60	$109.60
Purchase #5	$164.59	11.618%	$183.7121	$183.71	$183.70	$183.70
Purchase #6	$50.64	10.343%	$55.8777	$55.88	$55.90	$55.90
Purchase #7	$164.70	10.623%	$182.1961	$182.20	$182.20	$182.20
7 purchase totals =	$1,008.40		$1,079.4187	$1,079.42	$1,079.40	$1,079.50