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	$176.77	5.352%	$186.2307	$186.23	$186.25	$186.20
Purchase #2	$56.84	8.862%	$61.8772	$61.88	$61.90	$61.90
Purchase #3	$75.73	13.443%	$85.9104	$85.91	$85.90	$85.90
Purchase #4	$209.61	6.580%	$223.4023	$223.40	$223.40	$223.40
Purchase #5	$61.32	5.870%	$64.9195	$64.92	$64.90	$64.90
Purchase #6	$131.65	7.743%	$141.8437	$141.84	$141.85	$141.80
Purchase #7	$199.40	5.719%	$210.8037	$210.80	$210.80	$210.80
7 purchase totals =	$911.32		$974.9875	$974.98	$975.00	$974.90