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	$127.61	4.867%	$133.8208	$133.82	$133.80	$133.80
Purchase #2	$85.33	4.640%	$89.2893	$89.29	$89.30	$89.30
Purchase #3	$47.82	11.596%	$53.3652	$53.37	$53.35	$53.40
Purchase #4	$96.87	9.136%	$105.72	$105.72	$105.70	$105.70
Purchase #5	$153.99	11.308%	$171.4032	$171.40	$171.40	$171.40
Purchase #6	$51.64	5.514%	$54.4874	$54.49	$54.50	$54.50
Purchase #7	$92.60	12.477%	$104.1537	$104.15	$104.15	$104.20
7 purchase totals =	$655.86		$712.2396	$712.24	$712.20	$712.30