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	$62.71	13.682%	$71.29	$71.29	$71.30	$71.30
Purchase #2	$39.31	6.704%	$41.9453	$41.95	$41.95	$41.90
Purchase #3	$18.77	11.282%	$20.8876	$20.89	$20.90	$20.90
Purchase #4	$196.77	4.393%	$205.4141	$205.41	$205.40	$205.40
Purchase #5	$94.64	9.422%	$103.557	$103.56	$103.55	$103.60
Purchase #6	$187.69	10.420%	$207.2473	$207.25	$207.25	$207.20
Purchase #7	$171.92	13.284%	$194.7579	$194.76	$194.75	$194.80
7 purchase totals =	$771.81		$845.0992	$845.11	$845.10	$845.10