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	$192.61	10.229%	$212.3121	$212.31	$212.30	$212.30
Purchase #2	$241.26	10.816%	$267.3547	$267.35	$267.35	$267.40
Purchase #3	$62.63	4.621%	$65.5241	$65.52	$65.50	$65.50
Purchase #4	$242.89	6.779%	$259.3555	$259.36	$259.35	$259.40
Purchase #5	$80.95	13.819%	$92.1365	$92.14	$92.15	$92.10
Purchase #6	$124.44	5.566%	$131.3663	$131.37	$131.35	$131.40
Purchase #7	$18.47	9.687%	$20.2592	$20.26	$20.25	$20.30
7 purchase totals =	$963.25		$1,048.3084	$1,048.31	$1,048.25	$1,048.40