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	$209.57	11.192%	$233.0251	$233.03	$233.05	$233.00
Purchase #2	$5.46	4.330%	$5.6964	$5.70	$5.70	$5.70
Purchase #3	$86.45	4.757%	$90.5624	$90.56	$90.55	$90.60
Purchase #4	$219.69	4.609%	$229.8155	$229.82	$229.80	$229.80
Purchase #5	$64.62	12.869%	$72.9359	$72.94	$72.95	$72.90
Purchase #6	$69.34	12.492%	$78.002	$78.00	$78.00	$78.00
Purchase #7	$92.93	13.521%	$105.4951	$105.50	$105.50	$105.50
7 purchase totals =	$748.06		$815.5324	$815.55	$815.55	$815.50