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	$208.26	3.531%	$215.6137	$215.61	$215.60	$215.60
Purchase #2	$158.32	8.171%	$171.2563	$171.26	$171.25	$171.30
Purchase #3	$67.33	8.707%	$73.1924	$73.19	$73.20	$73.20
Purchase #4	$79.64	7.860%	$85.8997	$85.90	$85.90	$85.90
Purchase #5	$77.33	10.657%	$85.5711	$85.57	$85.55	$85.60
Purchase #6	$134.73	13.618%	$153.0775	$153.08	$153.10	$153.10
Purchase #7	$248.82	12.259%	$279.3228	$279.32	$279.30	$279.30
7 purchase totals =	$974.43		$1,063.9335	$1,063.93	$1,063.90	$1,064.00