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	$178.45	13.406%	$202.373	$202.37	$202.35	$202.40
Purchase #2	$78.56	9.189%	$85.7789	$85.78	$85.80	$85.80
Purchase #3	$232.78	8.818%	$253.3065	$253.31	$253.30	$253.30
Purchase #4	$103.75	5.167%	$109.1108	$109.11	$109.10	$109.10
Purchase #5	$128.56	13.186%	$145.5119	$145.51	$145.50	$145.50
Purchase #6	$40.94	4.552%	$42.8036	$42.80	$42.80	$42.80
Purchase #7	$154.97	7.300%	$166.2828	$166.28	$166.30	$166.30
7 purchase totals =	$918.01		$1,005.1675	$1,005.16	$1,005.15	$1,005.20