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	$181.64	8.242%	$196.6108	$196.61	$196.60	$196.60
Purchase #2	$170.75	13.540%	$193.8696	$193.87	$193.85	$193.90
Purchase #3	$229.36	12.820%	$258.764	$258.76	$258.75	$258.80
Purchase #4	$209.39	11.373%	$233.2039	$233.20	$233.20	$233.20
Purchase #5	$57.46	3.326%	$59.3711	$59.37	$59.35	$59.40
Purchase #6	$233.42	10.426%	$257.7564	$257.76	$257.75	$257.80
Purchase #7	$69.95	11.674%	$78.116	$78.12	$78.10	$78.10
7 purchase totals =	$1,151.97		$1,277.6918	$1,277.69	$1,277.60	$1,277.80