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	$18.89	5.482%	$19.9255	$19.93	$19.95	$19.90
Purchase #2	$50.77	3.665%	$52.6307	$52.63	$52.65	$52.60
Purchase #3	$182.47	9.271%	$199.3868	$199.39	$199.40	$199.40
Purchase #4	$140.56	4.533%	$146.9316	$146.93	$146.95	$146.90
Purchase #5	$105.46	5.385%	$111.139	$111.14	$111.15	$111.10
Purchase #6	$202.28	11.293%	$225.1235	$225.12	$225.10	$225.10
Purchase #7	$242.27	11.158%	$269.3025	$269.30	$269.30	$269.30
7 purchase totals =	$942.70		$1,024.4396	$1,024.44	$1,024.50	$1,024.30