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	$164.75	4.137%	$171.5657	$171.57	$171.55	$171.60
Purchase #2	$50.30	4.310%	$52.4679	$52.47	$52.45	$52.50
Purchase #3	$68.88	3.815%	$71.5078	$71.51	$71.50	$71.50
Purchase #4	$49.57	7.705%	$53.3894	$53.39	$53.40	$53.40
Purchase #5	$115.38	12.350%	$129.6294	$129.63	$129.65	$129.60
Purchase #6	$45.33	7.624%	$48.786	$48.79	$48.80	$48.80
Purchase #7	$243.34	10.528%	$268.9588	$268.96	$268.95	$269.00
7 purchase totals =	$737.55		$796.3050	$796.32	$796.30	$796.40