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	$177.63	5.552%	$187.492	$187.49	$187.50	$187.50
Purchase #2	$112.97	13.146%	$127.821	$127.82	$127.80	$127.80
Purchase #3	$236.51	11.307%	$263.2522	$263.25	$263.25	$263.30
Purchase #4	$250.62	9.621%	$274.7322	$274.73	$274.75	$274.70
Purchase #5	$79.51	5.534%	$83.9101	$83.91	$83.90	$83.90
Purchase #6	$240.61	5.755%	$254.4571	$254.46	$254.45	$254.50
Purchase #7	$64.89	9.445%	$71.0189	$71.02	$71.00	$71.00
7 purchase totals =	$1,162.74		$1,262.6835	$1,262.68	$1,262.65	$1,262.70