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	$153.48	13.712%	$174.5252	$174.53	$174.55	$174.50
Purchase #2	$33.40	11.794%	$37.3392	$37.34	$37.35	$37.30
Purchase #3	$104.72	7.655%	$112.7363	$112.74	$112.75	$112.70
Purchase #4	$136.28	13.254%	$154.3426	$154.34	$154.35	$154.30
Purchase #5	$89.71	7.372%	$96.3234	$96.32	$96.30	$96.30
Purchase #6	$119.77	10.411%	$132.2393	$132.24	$132.25	$132.20
Purchase #7	$76.25	4.840%	$79.9405	$79.94	$79.95	$79.90
7 purchase totals =	$713.61		$787.4465	$787.45	$787.50	$787.20