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	$61.89	5.809%	$65.4852	$65.49	$65.50	$65.50
Purchase #2	$96.72	13.224%	$109.5103	$109.51	$109.50	$109.50
Purchase #3	$10.29	10.586%	$11.3793	$11.38	$11.40	$11.40
Purchase #4	$5.45	11.106%	$6.0553	$6.06	$6.05	$6.10
Purchase #5	$166.89	10.264%	$184.0196	$184.02	$184.00	$184.00
Purchase #6	$161.37	10.831%	$178.848	$178.85	$178.85	$178.80
Purchase #7	$33.49	10.646%	$37.0553	$37.06	$37.05	$37.10
7 purchase totals =	$536.10		$592.3530	$592.37	$592.35	$592.40