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	$93.53	9.425%	$102.3452	$102.35	$102.35	$102.30
Purchase #2	$150.25	3.173%	$155.0174	$155.02	$155.00	$155.00
Purchase #3	$85.29	9.825%	$93.6697	$93.67	$93.65	$93.70
Purchase #4	$91.74	7.124%	$98.2756	$98.28	$98.30	$98.30
Purchase #5	$103.91	7.279%	$111.4736	$111.47	$111.45	$111.50
Purchase #6	$178.69	7.858%	$192.7315	$192.73	$192.75	$192.70
Purchase #7	$134.31	3.771%	$139.3748	$139.37	$139.35	$139.40
7 purchase totals =	$837.72		$892.8878	$892.89	$892.85	$892.90