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	$31.79	4.515%	$33.2253	$33.23	$33.25	$33.20
Purchase #2	$230.35	3.725%	$238.9305	$238.93	$238.95	$238.90
Purchase #3	$73.60	12.174%	$82.5601	$82.56	$82.55	$82.60
Purchase #4	$234.32	3.825%	$243.2827	$243.28	$243.30	$243.30
Purchase #5	$92.99	8.435%	$100.8337	$100.83	$100.85	$100.80
Purchase #6	$107.71	7.130%	$115.3897	$115.39	$115.40	$115.40
Purchase #7	$189.98	6.618%	$202.5529	$202.55	$202.55	$202.60
7 purchase totals =	$960.74		$1,016.7749	$1,016.77	$1,016.85	$1,016.80