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	$145.64	4.545%	$152.2593	$152.26	$152.25	$152.30
Purchase #2	$166.40	9.149%	$181.6239	$181.62	$181.60	$181.60
Purchase #3	$100.48	6.293%	$106.8032	$106.80	$106.80	$106.80
Purchase #4	$74.96	4.836%	$78.5851	$78.59	$78.60	$78.60
Purchase #5	$128.45	10.817%	$142.3444	$142.34	$142.35	$142.30
Purchase #6	$180.73	12.553%	$203.417	$203.42	$203.40	$203.40
Purchase #7	$204.74	11.104%	$227.4743	$227.47	$227.45	$227.50
7 purchase totals =	$1,001.40		$1,092.5072	$1,092.50	$1,092.45	$1,092.50