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	$248.71	13.535%	$282.3729	$282.37	$282.35	$282.40
Purchase #2	$78.59	13.570%	$89.2547	$89.25	$89.25	$89.30
Purchase #3	$144.83	7.185%	$155.236	$155.24	$155.25	$155.20
Purchase #4	$96.88	6.805%	$103.4727	$103.47	$103.45	$103.50
Purchase #5	$204.29	3.805%	$212.0632	$212.06	$212.05	$212.10
Purchase #6	$56.39	4.125%	$58.7161	$58.72	$58.70	$58.70
Purchase #7	$221.55	12.155%	$248.4794	$248.48	$248.50	$248.50
7 purchase totals =	$1,051.24		$1,149.5950	$1,149.59	$1,149.55	$1,149.70