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	$61.31	4.782%	$64.2418	$64.24	$64.25	$64.20
Purchase #2	$117.32	8.556%	$127.3579	$127.36	$127.35	$127.40
Purchase #3	$229.78	6.861%	$245.5452	$245.55	$245.55	$245.50
Purchase #4	$206.88	8.412%	$224.2827	$224.28	$224.30	$224.30
Purchase #5	$119.78	3.145%	$123.5471	$123.55	$123.55	$123.50
Purchase #6	$239.59	5.370%	$252.456	$252.46	$252.45	$252.50
Purchase #7	$97.83	5.525%	$103.2351	$103.24	$103.25	$103.20
7 purchase totals =	$1,072.49		$1,140.6658	$1,140.68	$1,140.70	$1,140.60