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	$22.79	10.482%	$25.1788	$25.18	$25.20	$25.20
Purchase #2	$152.47	9.795%	$167.4044	$167.40	$167.40	$167.40
Purchase #3	$240.35	7.480%	$258.3282	$258.33	$258.35	$258.30
Purchase #4	$100.56	4.672%	$105.2582	$105.26	$105.25	$105.30
Purchase #5	$108.53	6.747%	$115.8525	$115.85	$115.85	$115.90
Purchase #6	$174.80	7.820%	$188.4694	$188.47	$188.45	$188.50
Purchase #7	$76.68	7.379%	$82.3382	$82.34	$82.35	$82.30
7 purchase totals =	$876.18		$942.8297	$942.83	$942.85	$942.90