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	$166.50	9.267%	$181.9296	$181.93	$181.95	$181.90
Purchase #2	$141.89	7.478%	$152.5005	$152.50	$152.50	$152.50
Purchase #3	$180.50	4.118%	$187.933	$187.93	$187.95	$187.90
Purchase #4	$166.59	12.197%	$186.909	$186.91	$186.90	$186.90
Purchase #5	$62.93	10.507%	$69.5421	$69.54	$69.55	$69.50
Purchase #6	$181.96	3.454%	$188.2449	$188.24	$188.25	$188.20
Purchase #7	$145.53	4.240%	$151.7005	$151.70	$151.70	$151.70
7 purchase totals =	$1,045.90		$1,118.7596	$1,118.75	$1,118.80	$1,118.60