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	$123.68	6.369%	$131.5572	$131.56	$131.55	$131.60
Purchase #2	$55.51	7.869%	$59.8781	$59.88	$59.90	$59.90
Purchase #3	$249.88	3.304%	$258.136	$258.14	$258.15	$258.10
Purchase #4	$48.65	5.483%	$51.3175	$51.32	$51.30	$51.30
Purchase #5	$212.58	11.728%	$237.5114	$237.51	$237.50	$237.50
Purchase #6	$186.71	12.308%	$209.6903	$209.69	$209.70	$209.70
Purchase #7	$194.58	5.860%	$205.9824	$205.98	$206.00	$206.00
7 purchase totals =	$1,071.59		$1,154.0729	$1,154.08	$1,154.10	$1,154.10