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	$88.41	11.332%	$98.4286	$98.43	$98.45	$98.40
Purchase #2	$119.77	6.755%	$127.8605	$127.86	$127.85	$127.90
Purchase #3	$144.27	12.358%	$162.0989	$162.10	$162.10	$162.10
Purchase #4	$21.30	3.118%	$21.9641	$21.96	$21.95	$22.00
Purchase #5	$203.83	12.514%	$229.3373	$229.34	$229.35	$229.30
Purchase #6	$207.30	9.462%	$226.9147	$226.91	$226.90	$226.90
Purchase #7	$74.39	5.253%	$78.2977	$78.30	$78.30	$78.30
7 purchase totals =	$859.27		$944.9018	$944.90	$944.90	$944.90