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	$178.36	4.691%	$186.7269	$186.73	$186.75	$186.70
Purchase #2	$55.91	12.128%	$62.6908	$62.69	$62.70	$62.70
Purchase #3	$56.28	6.453%	$59.9117	$59.91	$59.90	$59.90
Purchase #4	$184.70	11.165%	$205.3218	$205.32	$205.30	$205.30
Purchase #5	$164.76	12.365%	$185.1326	$185.13	$185.15	$185.10
Purchase #6	$246.27	5.439%	$259.6646	$259.66	$259.65	$259.70
Purchase #7	$92.84	9.188%	$101.3701	$101.37	$101.35	$101.40
7 purchase totals =	$979.12		$1,060.8185	$1,060.81	$1,060.80	$1,060.80