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	$103.62	11.361%	$115.3923	$115.39	$115.40	$115.40
Purchase #2	$99.49	9.658%	$109.0987	$109.10	$109.10	$109.10
Purchase #3	$80.82	12.345%	$90.7972	$90.80	$90.80	$90.80
Purchase #4	$221.77	5.554%	$234.0871	$234.09	$234.10	$234.10
Purchase #5	$167.30	9.657%	$183.4562	$183.46	$183.45	$183.50
Purchase #6	$101.32	4.259%	$105.6352	$105.64	$105.65	$105.60
Purchase #7	$168.56	13.484%	$191.2886	$191.29	$191.30	$191.30
7 purchase totals =	$942.88		$1,029.7553	$1,029.77	$1,029.80	$1,029.80