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	$43.56	8.124%	$47.0988	$47.10	$47.10	$47.10
Purchase #2	$12.63	6.580%	$13.4611	$13.46	$13.45	$13.50
Purchase #3	$203.44	8.267%	$220.2584	$220.26	$220.25	$220.30
Purchase #4	$107.28	5.210%	$112.8693	$112.87	$112.85	$112.90
Purchase #5	$223.82	11.681%	$249.9644	$249.96	$249.95	$250.00
Purchase #6	$98.94	12.521%	$111.3283	$111.33	$111.35	$111.30
Purchase #7	$249.46	12.573%	$280.8246	$280.82	$280.80	$280.80
7 purchase totals =	$939.13		$1,035.8049	$1,035.80	$1,035.75	$1,035.90