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	$100.70	13.587%	$114.3821	$114.38	$114.40	$114.40
Purchase #2	$89.74	10.862%	$99.4876	$99.49	$99.50	$99.50
Purchase #3	$181.89	9.757%	$199.637	$199.64	$199.65	$199.60
Purchase #4	$66.66	5.645%	$70.423	$70.42	$70.40	$70.40
Purchase #5	$82.31	11.530%	$91.8003	$91.80	$91.80	$91.80
Purchase #6	$121.91	4.524%	$127.4252	$127.43	$127.45	$127.40
Purchase #7	$35.65	8.194%	$38.5712	$38.57	$38.55	$38.60
7 purchase totals =	$678.86		$741.7264	$741.73	$741.75	$741.70