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	$237.70	13.133%	$268.9171	$268.92	$268.90	$268.90
Purchase #2	$183.45	3.291%	$189.4873	$189.49	$189.50	$189.50
Purchase #3	$84.70	7.203%	$90.8009	$90.80	$90.80	$90.80
Purchase #4	$68.41	11.791%	$76.4762	$76.48	$76.50	$76.50
Purchase #5	$92.58	13.585%	$105.157	$105.16	$105.15	$105.20
Purchase #6	$241.59	9.211%	$263.8429	$263.84	$263.85	$263.80
Purchase #7	$101.65	3.843%	$105.5564	$105.56	$105.55	$105.60
7 purchase totals =	$1,010.08		$1,100.2378	$1,100.25	$1,100.25	$1,100.30