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	$249.32	7.381%	$267.7223	$267.72	$267.70	$267.70
Purchase #2	$83.61	8.560%	$90.767	$90.77	$90.75	$90.80
Purchase #3	$140.83	9.373%	$154.03	$154.03	$154.05	$154.00
Purchase #4	$187.44	10.335%	$206.8119	$206.81	$206.80	$206.80
Purchase #5	$96.98	11.386%	$108.0221	$108.02	$108.00	$108.00
Purchase #6	$128.71	12.177%	$144.383	$144.38	$144.40	$144.40
Purchase #7	$127.57	3.107%	$131.5336	$131.53	$131.55	$131.50
7 purchase totals =	$1,014.46		$1,103.2699	$1,103.26	$1,103.25	$1,103.20