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	$116.28	10.270%	$128.222	$128.22	$128.20	$128.20
Purchase #2	$64.31	3.804%	$66.7564	$66.76	$66.75	$66.80
Purchase #3	$166.46	12.632%	$187.4872	$187.49	$187.50	$187.50
Purchase #4	$228.29	4.278%	$238.0562	$238.06	$238.05	$238.10
Purchase #5	$60.96	9.769%	$66.9152	$66.92	$66.90	$66.90
Purchase #6	$212.73	11.566%	$237.3344	$237.33	$237.35	$237.30
Purchase #7	$114.28	11.185%	$127.0622	$127.06	$127.05	$127.10
7 purchase totals =	$963.31		$1,051.8336	$1,051.84	$1,051.80	$1,051.90