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	$211.56	12.209%	$237.3894	$237.39	$237.40	$237.40
Purchase #2	$232.68	6.529%	$247.8717	$247.87	$247.85	$247.90
Purchase #3	$162.49	7.250%	$174.2705	$174.27	$174.25	$174.30
Purchase #4	$185.39	4.779%	$194.2498	$194.25	$194.25	$194.20
Purchase #5	$37.66	8.619%	$40.9059	$40.91	$40.90	$40.90
Purchase #6	$84.69	5.802%	$89.6037	$89.60	$89.60	$89.60
Purchase #7	$168.58	13.802%	$191.8474	$191.85	$191.85	$191.80
7 purchase totals =	$1,083.05		$1,176.1384	$1,176.14	$1,176.10	$1,176.10