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	$184.87	12.503%	$207.9843	$207.98	$208.00	$208.00
Purchase #2	$89.73	3.451%	$92.8266	$92.83	$92.85	$92.80
Purchase #3	$117.56	8.309%	$127.3281	$127.33	$127.35	$127.30
Purchase #4	$86.76	9.259%	$94.7931	$94.79	$94.80	$94.80
Purchase #5	$177.69	4.657%	$185.965	$185.97	$185.95	$186.00
Purchase #6	$206.39	11.650%	$230.4344	$230.43	$230.45	$230.40
Purchase #7	$61.50	9.745%	$67.4932	$67.49	$67.50	$67.50
7 purchase totals =	$924.50		$1,006.8247	$1,006.82	$1,006.90	$1,006.80