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	$185.82	5.790%	$196.579	$196.58	$196.60	$196.60
Purchase #2	$51.39	12.688%	$57.9104	$57.91	$57.90	$57.90
Purchase #3	$101.80	7.520%	$109.4554	$109.46	$109.45	$109.50
Purchase #4	$72.37	13.502%	$82.1414	$82.14	$82.15	$82.10
Purchase #5	$203.71	5.255%	$214.415	$214.42	$214.40	$214.40
Purchase #6	$109.72	13.681%	$124.7308	$124.73	$124.75	$124.70
Purchase #7	$105.92	4.708%	$110.9067	$110.91	$110.90	$110.90
7 purchase totals =	$830.73		$896.1387	$896.15	$896.15	$896.10