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	$246.26	9.119%	$268.7164	$268.72	$268.70	$268.70
Purchase #2	$19.40	4.829%	$20.3368	$20.34	$20.35	$20.30
Purchase #3	$53.25	3.432%	$55.0775	$55.08	$55.10	$55.10
Purchase #4	$72.87	12.865%	$82.2447	$82.24	$82.25	$82.20
Purchase #5	$49.37	10.681%	$54.6432	$54.64	$54.65	$54.60
Purchase #6	$97.80	12.437%	$109.9634	$109.96	$109.95	$110.00
Purchase #7	$142.27	13.581%	$161.5917	$161.59	$161.60	$161.60
7 purchase totals =	$681.22		$752.5737	$752.57	$752.60	$752.50