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	$213.35	6.804%	$227.8663	$227.87	$227.85	$227.90
Purchase #2	$163.93	6.696%	$174.9068	$174.91	$174.90	$174.90
Purchase #3	$117.94	13.736%	$134.1402	$134.14	$134.15	$134.10
Purchase #4	$171.36	13.346%	$194.2297	$194.23	$194.25	$194.20
Purchase #5	$35.89	5.394%	$37.8259	$37.83	$37.85	$37.80
Purchase #6	$154.25	11.178%	$171.4921	$171.49	$171.50	$171.50
Purchase #7	$70.53	9.520%	$77.2445	$77.24	$77.25	$77.20
7 purchase totals =	$927.25		$1,017.7055	$1,017.71	$1,017.75	$1,017.60