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	$181.59	5.644%	$191.8389	$191.84	$191.85	$191.80
Purchase #2	$59.77	6.830%	$63.8523	$63.85	$63.85	$63.90
Purchase #3	$212.70	4.152%	$221.5313	$221.53	$221.55	$221.50
Purchase #4	$148.37	4.681%	$155.3152	$155.32	$155.30	$155.30
Purchase #5	$42.94	9.868%	$47.1773	$47.18	$47.20	$47.20
Purchase #6	$145.64	11.831%	$162.8707	$162.87	$162.85	$162.90
Purchase #7	$163.25	5.783%	$172.6907	$172.69	$172.70	$172.70
7 purchase totals =	$954.26		$1,015.2764	$1,015.28	$1,015.30	$1,015.30