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	$174.66	4.247%	$182.0778	$182.08	$182.10	$182.10
Purchase #2	$53.86	10.113%	$59.3069	$59.31	$59.30	$59.30
Purchase #3	$144.57	13.747%	$164.444	$164.44	$164.45	$164.40
Purchase #4	$151.55	11.302%	$168.6782	$168.68	$168.70	$168.70
Purchase #5	$221.71	8.650%	$240.8879	$240.89	$240.90	$240.90
Purchase #6	$153.70	7.755%	$165.6194	$165.62	$165.60	$165.60
Purchase #7	$209.79	6.457%	$223.3361	$223.34	$223.35	$223.30
7 purchase totals =	$1,109.84		$1,204.3503	$1,204.36	$1,204.40	$1,204.30