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	$53.49	3.554%	$55.391	$55.39	$55.40	$55.40
Purchase #2	$81.71	4.550%	$85.4278	$85.43	$85.45	$85.40
Purchase #3	$77.83	12.869%	$87.8459	$87.85	$87.85	$87.80
Purchase #4	$185.62	4.670%	$194.2885	$194.29	$194.30	$194.30
Purchase #5	$57.44	8.364%	$62.2443	$62.24	$62.25	$62.20
Purchase #6	$150.73	3.766%	$156.4065	$156.41	$156.40	$156.40
Purchase #7	$85.84	7.199%	$92.0196	$92.02	$92.00	$92.00
7 purchase totals =	$692.66		$733.6236	$733.63	$733.65	$733.50