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	$63.97	13.263%	$72.4543	$72.45	$72.45	$72.50
Purchase #2	$181.59	13.194%	$205.549	$205.55	$205.55	$205.50
Purchase #3	$133.63	7.471%	$143.6135	$143.61	$143.60	$143.60
Purchase #4	$79.64	8.557%	$86.4548	$86.45	$86.45	$86.50
Purchase #5	$148.69	3.222%	$153.4808	$153.48	$153.50	$153.50
Purchase #6	$61.92	4.621%	$64.7813	$64.78	$64.80	$64.80
Purchase #7	$211.71	11.246%	$235.5189	$235.52	$235.50	$235.50
7 purchase totals =	$881.15		$961.8526	$961.84	$961.85	$961.90