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	$174.69	5.607%	$184.4849	$184.48	$184.50	$184.50
Purchase #2	$190.48	3.320%	$196.8039	$196.80	$196.80	$196.80
Purchase #3	$196.77	7.266%	$211.0673	$211.07	$211.05	$211.10
Purchase #4	$78.78	10.241%	$86.8479	$86.85	$86.85	$86.80
Purchase #5	$30.56	7.299%	$32.7906	$32.79	$32.80	$32.80
Purchase #6	$235.94	6.753%	$251.873	$251.87	$251.85	$251.90
Purchase #7	$158.36	10.465%	$174.9324	$174.93	$174.95	$174.90
7 purchase totals =	$1,065.58		$1,138.8000	$1,138.79	$1,138.80	$1,138.80