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	$166.92	7.415%	$179.2971	$179.30	$179.30	$179.30
Purchase #2	$31.64	6.148%	$33.5852	$33.59	$33.60	$33.60
Purchase #3	$176.46	6.860%	$188.5652	$188.57	$188.55	$188.60
Purchase #4	$33.98	9.725%	$37.2846	$37.28	$37.30	$37.30
Purchase #5	$97.51	12.427%	$109.6276	$109.63	$109.65	$109.60
Purchase #6	$193.42	12.731%	$218.0443	$218.04	$218.05	$218.00
Purchase #7	$52.66	7.522%	$56.6211	$56.62	$56.60	$56.60
7 purchase totals =	$752.59		$823.0251	$823.03	$823.05	$823.00