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	$174.58	12.722%	$196.7901	$196.79	$196.80	$196.80
Purchase #2	$245.99	6.757%	$262.6115	$262.61	$262.60	$262.60
Purchase #3	$36.30	10.349%	$40.0567	$40.06	$40.05	$40.10
Purchase #4	$169.89	11.400%	$189.2575	$189.26	$189.25	$189.30
Purchase #5	$161.30	10.632%	$178.4494	$178.45	$178.45	$178.40
Purchase #6	$145.48	6.270%	$154.6016	$154.60	$154.60	$154.60
Purchase #7	$125.64	4.223%	$130.9458	$130.95	$130.95	$130.90
7 purchase totals =	$1,059.18		$1,152.7126	$1,152.72	$1,152.70	$1,152.70