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	$186.82	4.243%	$194.7468	$194.75	$194.75	$194.70
Purchase #2	$229.36	11.780%	$256.3786	$256.38	$256.40	$256.40
Purchase #3	$174.93	5.481%	$184.5179	$184.52	$184.50	$184.50
Purchase #4	$35.57	13.653%	$40.4264	$40.43	$40.45	$40.40
Purchase #5	$113.32	6.734%	$120.951	$120.95	$120.95	$121.00
Purchase #6	$81.31	12.566%	$91.5274	$91.53	$91.55	$91.50
Purchase #7	$217.27	9.830%	$238.6276	$238.63	$238.65	$238.60
7 purchase totals =	$1,038.58		$1,127.1757	$1,127.19	$1,127.25	$1,127.10