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	$78.41	6.110%	$83.2009	$83.20	$83.20	$83.20
Purchase #2	$95.29	4.607%	$99.68	$99.68	$99.70	$99.70
Purchase #3	$128.47	10.737%	$142.2638	$142.26	$142.25	$142.30
Purchase #4	$235.31	4.589%	$246.1084	$246.11	$246.10	$246.10
Purchase #5	$107.71	3.566%	$111.5509	$111.55	$111.55	$111.60
Purchase #6	$84.75	5.858%	$89.7147	$89.71	$89.70	$89.70
Purchase #7	$236.78	4.234%	$246.8053	$246.81	$246.80	$246.80
7 purchase totals =	$966.72		$1,019.3240	$1,019.32	$1,019.30	$1,019.40