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	$159.73	3.454%	$165.2471	$165.25	$165.25	$165.20
Purchase #2	$164.74	11.121%	$183.0607	$183.06	$183.05	$183.10
Purchase #3	$202.37	8.656%	$219.8871	$219.89	$219.90	$219.90
Purchase #4	$156.91	9.162%	$171.2861	$171.29	$171.30	$171.30
Purchase #5	$20.61	3.684%	$21.3693	$21.37	$21.35	$21.40
Purchase #6	$96.63	5.472%	$101.9176	$101.92	$101.90	$101.90
Purchase #7	$222.92	6.859%	$238.2101	$238.21	$238.20	$238.20
7 purchase totals =	$1,023.91		$1,100.9780	$1,100.99	$1,100.95	$1,101.00