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	$69.95	10.654%	$77.4025	$77.40	$77.40	$77.40
Purchase #2	$194.87	4.361%	$203.3683	$203.37	$203.35	$203.40
Purchase #3	$210.78	11.453%	$234.9206	$234.92	$234.90	$234.90
Purchase #4	$75.76	3.366%	$78.3101	$78.31	$78.30	$78.30
Purchase #5	$215.38	6.315%	$228.9812	$228.98	$229.00	$229.00
Purchase #6	$112.43	4.463%	$117.4478	$117.45	$117.45	$117.40
Purchase #7	$115.56	10.253%	$127.4084	$127.41	$127.40	$127.40
7 purchase totals =	$994.73		$1,067.8389	$1,067.84	$1,067.80	$1,067.80