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	$181.59	4.692%	$190.1102	$190.11	$190.10	$190.10
Purchase #2	$63.63	5.103%	$66.877	$66.88	$66.90	$66.90
Purchase #3	$91.54	10.362%	$101.0254	$101.03	$101.05	$101.00
Purchase #4	$164.37	4.411%	$171.6204	$171.62	$171.60	$171.60
Purchase #5	$224.50	11.739%	$250.8541	$250.85	$250.85	$250.90
Purchase #6	$16.78	6.526%	$17.8751	$17.88	$17.90	$17.90
Purchase #7	$230.50	12.700%	$259.7735	$259.77	$259.75	$259.80
7 purchase totals =	$972.91		$1,058.1357	$1,058.14	$1,058.15	$1,058.20