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	$179.78	10.142%	$198.0133	$198.01	$198.00	$198.00
Purchase #2	$21.98	13.452%	$24.9367	$24.94	$24.95	$24.90
Purchase #3	$78.31	9.686%	$85.8951	$85.90	$85.90	$85.90
Purchase #4	$56.73	9.553%	$62.1494	$62.15	$62.15	$62.10
Purchase #5	$120.84	5.361%	$127.3182	$127.32	$127.30	$127.30
Purchase #6	$235.45	4.295%	$245.5626	$245.56	$245.55	$245.60
Purchase #7	$24.26	9.467%	$26.5567	$26.56	$26.55	$26.60
7 purchase totals =	$717.35		$770.4320	$770.44	$770.40	$770.40