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	$226.33	3.488%	$234.2244	$234.22	$234.20	$234.20
Purchase #2	$239.78	6.693%	$255.8285	$255.83	$255.85	$255.80
Purchase #3	$110.72	8.506%	$120.1378	$120.14	$120.15	$120.10
Purchase #4	$168.83	11.785%	$188.7266	$188.73	$188.75	$188.70
Purchase #5	$74.65	9.677%	$81.8739	$81.87	$81.85	$81.90
Purchase #6	$166.34	7.751%	$179.233	$179.23	$179.25	$179.20
Purchase #7	$150.61	3.785%	$156.3106	$156.31	$156.30	$156.30
7 purchase totals =	$1,137.26		$1,216.3348	$1,216.33	$1,216.35	$1,216.20