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	$110.72	3.689%	$114.8045	$114.80	$114.80	$114.80
Purchase #2	$194.99	11.503%	$217.4197	$217.42	$217.40	$217.40
Purchase #3	$128.70	13.335%	$145.8621	$145.86	$145.85	$145.90
Purchase #4	$59.74	12.287%	$67.0803	$67.08	$67.10	$67.10
Purchase #5	$192.55	6.630%	$205.3161	$205.32	$205.30	$205.30
Purchase #6	$196.48	9.820%	$215.7743	$215.77	$215.75	$215.80
Purchase #7	$168.87	6.529%	$179.8955	$179.90	$179.90	$179.90
7 purchase totals =	$1,052.05		$1,146.1525	$1,146.15	$1,146.10	$1,146.20