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	$89.54	3.159%	$92.3686	$92.37	$92.35	$92.40
Purchase #2	$86.32	3.735%	$89.5441	$89.54	$89.55	$89.50
Purchase #3	$209.39	3.404%	$216.5176	$216.52	$216.50	$216.50
Purchase #4	$235.92	12.242%	$264.8013	$264.80	$264.80	$264.80
Purchase #5	$109.39	6.864%	$116.8985	$116.90	$116.90	$116.90
Purchase #6	$182.69	8.868%	$198.8909	$198.89	$198.90	$198.90
Purchase #7	$143.72	5.338%	$151.3918	$151.39	$151.40	$151.40
7 purchase totals =	$1,056.97		$1,130.4128	$1,130.41	$1,130.40	$1,130.40