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	$147.88	3.123%	$152.4983	$152.50	$152.50	$152.50
Purchase #2	$245.95	5.513%	$259.5092	$259.51	$259.50	$259.50
Purchase #3	$11.40	7.874%	$12.2976	$12.30	$12.30	$12.30
Purchase #4	$25.25	13.444%	$28.6446	$28.64	$28.65	$28.60
Purchase #5	$54.70	11.683%	$61.0906	$61.09	$61.10	$61.10
Purchase #6	$176.72	13.185%	$200.0205	$200.02	$200.00	$200.00
Purchase #7	$69.80	11.133%	$77.5708	$77.57	$77.55	$77.60
7 purchase totals =	$731.70		$791.6316	$791.63	$791.60	$791.60