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	$80.47	4.174%	$83.8288	$83.83	$83.85	$83.80
Purchase #2	$31.25	7.392%	$33.56	$33.56	$33.55	$33.60
Purchase #3	$164.52	4.253%	$171.517	$171.52	$171.50	$171.50
Purchase #4	$35.31	12.686%	$39.7894	$39.79	$39.80	$39.80
Purchase #5	$73.47	11.608%	$81.9984	$82.00	$82.00	$82.00
Purchase #6	$124.56	13.461%	$141.327	$141.33	$141.35	$141.30
Purchase #7	$179.84	6.434%	$191.4109	$191.41	$191.40	$191.40
7 purchase totals =	$689.42		$743.4315	$743.44	$743.45	$743.40