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	$227.98	6.873%	$243.6491	$243.65	$243.65	$243.60
Purchase #2	$124.60	7.216%	$133.5911	$133.59	$133.60	$133.60
Purchase #3	$143.85	7.328%	$154.3913	$154.39	$154.40	$154.40
Purchase #4	$181.94	4.498%	$190.1237	$190.12	$190.10	$190.10
Purchase #5	$243.50	10.317%	$268.6219	$268.62	$268.60	$268.60
Purchase #6	$217.26	12.409%	$244.2198	$244.22	$244.20	$244.20
Purchase #7	$86.78	4.661%	$90.8248	$90.82	$90.80	$90.80
7 purchase totals =	$1,225.91		$1,325.4217	$1,325.41	$1,325.35	$1,325.30