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	$147.30	4.500%	$153.9285	$153.93	$153.95	$153.90
Purchase #2	$80.52	7.457%	$86.5244	$86.52	$86.50	$86.50
Purchase #3	$52.29	12.790%	$58.9779	$58.98	$59.00	$59.00
Purchase #4	$64.52	10.746%	$71.4533	$71.45	$71.45	$71.50
Purchase #5	$126.95	10.586%	$140.3889	$140.39	$140.40	$140.40
Purchase #6	$85.84	4.568%	$89.7612	$89.76	$89.75	$89.80
Purchase #7	$62.99	10.811%	$69.7998	$69.80	$69.80	$69.80
7 purchase totals =	$620.41		$670.8340	$670.83	$670.85	$670.90