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	$64.44	4.529%	$67.3585	$67.36	$67.35	$67.40
Purchase #2	$225.95	10.368%	$249.3765	$249.38	$249.40	$249.40
Purchase #3	$119.30	3.360%	$123.3085	$123.31	$123.30	$123.30
Purchase #4	$197.99	13.294%	$224.3108	$224.31	$224.30	$224.30
Purchase #5	$19.53	11.573%	$21.7902	$21.79	$21.80	$21.80
Purchase #6	$170.84	12.120%	$191.5458	$191.55	$191.55	$191.50
Purchase #7	$179.89	4.809%	$188.5409	$188.54	$188.55	$188.50
7 purchase totals =	$977.94		$1,066.2312	$1,066.24	$1,066.25	$1,066.20