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	$165.44	6.652%	$176.4451	$176.45	$176.45	$176.40
Purchase #2	$229.80	3.640%	$238.1647	$238.16	$238.15	$238.20
Purchase #3	$158.33	13.808%	$180.1922	$180.19	$180.20	$180.20
Purchase #4	$90.38	6.506%	$96.2601	$96.26	$96.25	$96.30
Purchase #5	$194.34	3.404%	$200.9553	$200.96	$200.95	$201.00
Purchase #6	$78.31	5.129%	$82.3265	$82.33	$82.35	$82.30
Purchase #7	$179.89	10.279%	$198.3809	$198.38	$198.40	$198.40
7 purchase totals =	$1,096.49		$1,172.7248	$1,172.73	$1,172.75	$1,172.80