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	$98.87	3.631%	$102.46	$102.46	$102.45	$102.50
Purchase #2	$156.27	3.721%	$162.0848	$162.08	$162.10	$162.10
Purchase #3	$96.45	12.123%	$108.1426	$108.14	$108.15	$108.10
Purchase #4	$171.95	11.436%	$191.6142	$191.61	$191.60	$191.60
Purchase #5	$210.65	11.267%	$234.3839	$234.38	$234.40	$234.40
Purchase #6	$159.47	5.374%	$168.0399	$168.04	$168.05	$168.00
Purchase #7	$35.41	12.539%	$39.8501	$39.85	$39.85	$39.90
7 purchase totals =	$929.07		$1,006.5755	$1,006.56	$1,006.60	$1,006.60