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	$206.25	3.427%	$213.3182	$213.32	$213.30	$213.30
Purchase #2	$63.27	12.300%	$71.0522	$71.05	$71.05	$71.10
Purchase #3	$27.40	5.172%	$28.8171	$28.82	$28.80	$28.80
Purchase #4	$166.84	13.269%	$188.978	$188.98	$189.00	$189.00
Purchase #5	$120.96	5.362%	$127.4459	$127.45	$127.45	$127.40
Purchase #6	$88.67	6.320%	$94.2739	$94.27	$94.25	$94.30
Purchase #7	$170.43	10.307%	$187.9962	$188.00	$188.00	$188.00
7 purchase totals =	$843.82		$911.8815	$911.89	$911.85	$911.90