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	$203.76	7.761%	$219.5738	$219.57	$219.55	$219.60
Purchase #2	$245.52	9.188%	$268.0784	$268.08	$268.10	$268.10
Purchase #3	$143.51	7.556%	$154.3536	$154.35	$154.35	$154.40
Purchase #4	$124.51	12.281%	$139.8011	$139.80	$139.80	$139.80
Purchase #5	$151.51	9.766%	$166.3065	$166.31	$166.30	$166.30
Purchase #6	$100.60	13.759%	$114.4416	$114.44	$114.45	$114.40
Purchase #7	$28.39	11.264%	$31.5878	$31.59	$31.60	$31.60
7 purchase totals =	$997.80		$1,094.1428	$1,094.14	$1,094.15	$1,094.20