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	$158.90	3.674%	$164.738	$164.74	$164.75	$164.70
Purchase #2	$33.43	7.855%	$36.0559	$36.06	$36.05	$36.10
Purchase #3	$133.38	6.850%	$142.5165	$142.52	$142.50	$142.50
Purchase #4	$172.55	6.582%	$183.9072	$183.91	$183.90	$183.90
Purchase #5	$136.78	4.260%	$142.6068	$142.61	$142.60	$142.60
Purchase #6	$204.88	8.269%	$221.8215	$221.82	$221.80	$221.80
Purchase #7	$248.84	6.131%	$264.0964	$264.10	$264.10	$264.10
7 purchase totals =	$1,088.76		$1,155.7423	$1,155.76	$1,155.70	$1,155.70