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	$82.41	3.802%	$85.5432	$85.54	$85.55	$85.50
Purchase #2	$56.48	9.621%	$61.9139	$61.91	$61.90	$61.90
Purchase #3	$5.54	7.453%	$5.9529	$5.95	$5.95	$6.00
Purchase #4	$54.82	6.465%	$58.3641	$58.36	$58.35	$58.40
Purchase #5	$127.70	7.216%	$136.9148	$136.91	$136.90	$136.90
Purchase #6	$37.86	4.374%	$39.516	$39.52	$39.50	$39.50
Purchase #7	$119.45	12.543%	$134.4326	$134.43	$134.45	$134.40
7 purchase totals =	$484.26		$522.6375	$522.62	$522.60	$522.60