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	$134.29	4.474%	$140.2981	$140.30	$140.30	$140.30
Purchase #2	$35.62	13.177%	$40.3136	$40.31	$40.30	$40.30
Purchase #3	$41.75	9.779%	$45.8327	$45.83	$45.85	$45.80
Purchase #4	$80.85	5.241%	$85.0873	$85.09	$85.10	$85.10
Purchase #5	$167.27	10.618%	$185.0307	$185.03	$185.05	$185.00
Purchase #6	$59.46	5.198%	$62.5507	$62.55	$62.55	$62.60
Purchase #7	$119.25	4.452%	$124.559	$124.56	$124.55	$124.60
7 purchase totals =	$638.49		$683.6721	$683.67	$683.70	$683.70