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	$62.98	4.298%	$65.6869	$65.69	$65.70	$65.70
Purchase #2	$101.33	4.106%	$105.4906	$105.49	$105.50	$105.50
Purchase #3	$165.50	7.825%	$178.4504	$178.45	$178.45	$178.50
Purchase #4	$45.72	8.322%	$49.5248	$49.52	$49.50	$49.50
Purchase #5	$142.48	9.745%	$156.3647	$156.36	$156.35	$156.40
Purchase #6	$236.39	6.570%	$251.9208	$251.92	$251.90	$251.90
Purchase #7	$164.27	9.487%	$179.8543	$179.85	$179.85	$179.90
7 purchase totals =	$918.67		$987.2925	$987.28	$987.25	$987.40