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	$179.52	6.747%	$191.6322	$191.63	$191.65	$191.60
Purchase #2	$178.37	9.278%	$194.9192	$194.92	$194.90	$194.90
Purchase #3	$13.93	6.417%	$14.8239	$14.82	$14.80	$14.80
Purchase #4	$106.48	8.164%	$115.173	$115.17	$115.15	$115.20
Purchase #5	$190.69	11.453%	$212.5297	$212.53	$212.55	$212.50
Purchase #6	$83.83	6.731%	$89.4726	$89.47	$89.45	$89.50
Purchase #7	$75.28	10.672%	$83.3139	$83.31	$83.30	$83.30
7 purchase totals =	$828.10		$901.8645	$901.85	$901.80	$901.80