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	$203.34	5.832%	$215.1988	$215.20	$215.20	$215.20
Purchase #2	$185.69	6.330%	$197.4442	$197.44	$197.45	$197.40
Purchase #3	$104.76	6.321%	$111.3819	$111.38	$111.40	$111.40
Purchase #4	$75.61	12.477%	$85.0439	$85.04	$85.05	$85.00
Purchase #5	$236.83	8.560%	$257.1026	$257.10	$257.10	$257.10
Purchase #6	$86.75	3.860%	$90.0986	$90.10	$90.10	$90.10
Purchase #7	$167.77	4.645%	$175.5629	$175.56	$175.55	$175.60
7 purchase totals =	$1,060.75		$1,131.8329	$1,131.82	$1,131.85	$1,131.80