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	$247.45	8.826%	$269.2899	$269.29	$269.30	$269.30
Purchase #2	$80.61	12.693%	$90.8418	$90.84	$90.85	$90.80
Purchase #3	$150.36	4.307%	$156.836	$156.84	$156.85	$156.80
Purchase #4	$116.67	10.665%	$129.1129	$129.11	$129.10	$129.10
Purchase #5	$114.77	3.114%	$118.3439	$118.34	$118.35	$118.30
Purchase #6	$103.98	3.705%	$107.8325	$107.83	$107.85	$107.80
Purchase #7	$175.60	11.774%	$196.2751	$196.28	$196.30	$196.30
7 purchase totals =	$989.44		$1,068.5321	$1,068.53	$1,068.60	$1,068.40