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	$93.64	6.517%	$99.7425	$99.74	$99.75	$99.70
Purchase #2	$112.42	3.745%	$116.6301	$116.63	$116.65	$116.60
Purchase #3	$153.48	6.857%	$164.0041	$164.00	$164.00	$164.00
Purchase #4	$90.63	6.370%	$96.4031	$96.40	$96.40	$96.40
Purchase #5	$15.95	3.702%	$16.5405	$16.54	$16.55	$16.50
Purchase #6	$94.74	6.328%	$100.7351	$100.74	$100.75	$100.70
Purchase #7	$167.71	13.842%	$190.9244	$190.92	$190.90	$190.90
7 purchase totals =	$728.57		$784.9798	$784.97	$785.00	$784.80