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	$114.69	11.428%	$127.7968	$127.80	$127.80	$127.80
Purchase #2	$175.76	4.736%	$184.084	$184.08	$184.10	$184.10
Purchase #3	$186.83	11.106%	$207.5793	$207.58	$207.60	$207.60
Purchase #4	$211.63	10.275%	$233.375	$233.38	$233.40	$233.40
Purchase #5	$219.64	6.244%	$233.3543	$233.35	$233.35	$233.40
Purchase #6	$64.82	3.590%	$67.147	$67.15	$67.15	$67.10
Purchase #7	$153.87	9.396%	$168.3276	$168.33	$168.35	$168.30
7 purchase totals =	$1,127.24		$1,221.6640	$1,221.67	$1,221.75	$1,221.70