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	$128.37	11.694%	$143.3816	$143.38	$143.40	$143.40
Purchase #2	$56.56	12.847%	$63.8263	$63.83	$63.85	$63.80
Purchase #3	$192.70	8.850%	$209.754	$209.75	$209.75	$209.80
Purchase #4	$159.53	9.166%	$174.1525	$174.15	$174.15	$174.20
Purchase #5	$50.98	7.594%	$54.8514	$54.85	$54.85	$54.90
Purchase #6	$171.88	11.312%	$191.3231	$191.32	$191.30	$191.30
Purchase #7	$89.66	13.228%	$101.5202	$101.52	$101.50	$101.50
7 purchase totals =	$849.68		$938.8091	$938.80	$938.80	$938.90