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	$198.99	10.172%	$219.2313	$219.23	$219.25	$219.20
Purchase #2	$90.39	12.439%	$101.6336	$101.63	$101.65	$101.60
Purchase #3	$185.90	4.140%	$193.5963	$193.60	$193.60	$193.60
Purchase #4	$89.86	13.169%	$101.6937	$101.69	$101.70	$101.70
Purchase #5	$70.55	11.343%	$78.5525	$78.55	$78.55	$78.60
Purchase #6	$180.33	11.398%	$200.884	$200.88	$200.90	$200.90
Purchase #7	$78.38	5.608%	$82.7756	$82.78	$82.80	$82.80
7 purchase totals =	$894.40		$978.3670	$978.36	$978.45	$978.40