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	$207.36	7.800%	$223.5341	$223.53	$223.55	$223.50
Purchase #2	$104.59	13.701%	$118.9199	$118.92	$118.90	$118.90
Purchase #3	$162.65	3.204%	$167.8613	$167.86	$167.85	$167.90
Purchase #4	$220.42	9.257%	$240.8243	$240.82	$240.80	$240.80
Purchase #5	$247.27	3.873%	$256.8468	$256.85	$256.85	$256.80
Purchase #6	$82.82	10.340%	$91.3836	$91.38	$91.40	$91.40
Purchase #7	$19.62	3.483%	$20.3034	$20.30	$20.30	$20.30
7 purchase totals =	$1,044.73		$1,119.6734	$1,119.66	$1,119.65	$1,119.60