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	$198.74	12.109%	$222.8054	$222.81	$222.80	$222.80
Purchase #2	$31.60	5.670%	$33.3917	$33.39	$33.40	$33.40
Purchase #3	$95.69	4.331%	$99.8343	$99.83	$99.85	$99.80
Purchase #4	$180.37	7.720%	$194.2946	$194.29	$194.30	$194.30
Purchase #5	$123.84	6.846%	$132.3181	$132.32	$132.30	$132.30
Purchase #6	$27.60	13.432%	$31.3072	$31.31	$31.30	$31.30
Purchase #7	$225.88	6.489%	$240.5374	$240.54	$240.55	$240.50
7 purchase totals =	$883.72		$954.4887	$954.49	$954.50	$954.40