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	$157.82	13.803%	$179.6039	$179.60	$179.60	$179.60
Purchase #2	$127.89	6.661%	$136.4088	$136.41	$136.40	$136.40
Purchase #3	$214.31	4.114%	$223.1267	$223.13	$223.15	$223.10
Purchase #4	$212.92	12.399%	$239.32	$239.32	$239.30	$239.30
Purchase #5	$64.83	13.816%	$73.7869	$73.79	$73.80	$73.80
Purchase #6	$203.74	9.120%	$222.3211	$222.32	$222.30	$222.30
Purchase #7	$84.31	6.106%	$89.458	$89.46	$89.45	$89.50
7 purchase totals =	$1,065.82		$1,164.0254	$1,164.03	$1,164.00	$1,164.00