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	$42.82	9.145%	$46.7359	$46.74	$46.75	$46.70
Purchase #2	$135.47	4.789%	$141.9577	$141.96	$141.95	$142.00
Purchase #3	$227.40	5.694%	$240.3482	$240.35	$240.35	$240.30
Purchase #4	$61.39	3.131%	$63.3121	$63.31	$63.30	$63.30
Purchase #5	$79.88	13.113%	$90.3547	$90.35	$90.35	$90.40
Purchase #6	$175.50	9.662%	$192.4568	$192.46	$192.45	$192.50
Purchase #7	$207.93	7.844%	$224.24	$224.24	$224.25	$224.20
7 purchase totals =	$930.39		$999.4054	$999.41	$999.40	$999.40