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	$218.39	9.145%	$238.3618	$238.36	$238.35	$238.40
Purchase #2	$217.32	5.623%	$229.5399	$229.54	$229.55	$229.50
Purchase #3	$91.27	5.356%	$96.1584	$96.16	$96.15	$96.20
Purchase #4	$229.73	4.538%	$240.1551	$240.16	$240.15	$240.20
Purchase #5	$184.46	12.771%	$208.0174	$208.02	$208.00	$208.00
Purchase #6	$88.25	3.236%	$91.1058	$91.11	$91.10	$91.10
Purchase #7	$55.81	11.359%	$62.1495	$62.15	$62.15	$62.10
7 purchase totals =	$1,085.23		$1,165.4879	$1,165.50	$1,165.45	$1,165.50