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	$92.47	7.503%	$99.408	$99.41	$99.40	$99.40
Purchase #2	$118.55	13.442%	$134.4855	$134.49	$134.50	$134.50
Purchase #3	$145.39	4.740%	$152.2815	$152.28	$152.30	$152.30
Purchase #4	$213.63	12.365%	$240.0453	$240.05	$240.05	$240.00
Purchase #5	$126.45	11.375%	$140.8337	$140.83	$140.85	$140.80
Purchase #6	$212.79	7.448%	$228.6386	$228.64	$228.65	$228.60
Purchase #7	$149.48	8.738%	$162.5416	$162.54	$162.55	$162.50
7 purchase totals =	$1,058.76		$1,158.2342	$1,158.24	$1,158.30	$1,158.10