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	$191.70	4.572%	$200.4645	$200.46	$200.45	$200.50
Purchase #2	$107.81	4.457%	$112.6151	$112.62	$112.60	$112.60
Purchase #3	$56.66	9.686%	$62.1481	$62.15	$62.15	$62.10
Purchase #4	$32.30	10.592%	$35.7212	$35.72	$35.70	$35.70
Purchase #5	$137.61	11.112%	$152.9012	$152.90	$152.90	$152.90
Purchase #6	$235.93	5.271%	$248.3659	$248.37	$248.35	$248.40
Purchase #7	$106.79	12.746%	$120.4015	$120.40	$120.40	$120.40
7 purchase totals =	$868.80		$932.6175	$932.62	$932.55	$932.60