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	$241.69	8.551%	$262.3569	$262.36	$262.35	$262.40
Purchase #2	$98.71	10.152%	$108.731	$108.73	$108.75	$108.70
Purchase #3	$202.58	9.470%	$221.7643	$221.76	$221.75	$221.80
Purchase #4	$79.81	13.839%	$90.8549	$90.85	$90.85	$90.90
Purchase #5	$50.74	8.189%	$54.8951	$54.90	$54.90	$54.90
Purchase #6	$89.98	7.319%	$96.5656	$96.57	$96.55	$96.60
Purchase #7	$230.61	6.634%	$245.9087	$245.91	$245.90	$245.90
7 purchase totals =	$994.12		$1,081.0765	$1,081.08	$1,081.05	$1,081.20