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	$47.94	11.605%	$53.5034	$53.50	$53.50	$53.50
Purchase #2	$174.92	12.196%	$196.2532	$196.25	$196.25	$196.30
Purchase #3	$66.91	7.263%	$71.7697	$71.77	$71.75	$71.80
Purchase #4	$167.53	6.358%	$178.1816	$178.18	$178.20	$178.20
Purchase #5	$166.90	10.475%	$184.3828	$184.38	$184.40	$184.40
Purchase #6	$201.63	10.840%	$223.4867	$223.49	$223.50	$223.50
Purchase #7	$99.95	11.411%	$111.3553	$111.36	$111.35	$111.40
7 purchase totals =	$925.78		$1,018.9327	$1,018.93	$1,018.95	$1,019.10