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	$244.47	5.757%	$258.5441	$258.54	$258.55	$258.50
Purchase #2	$237.89	9.526%	$260.5514	$260.55	$260.55	$260.60
Purchase #3	$10.25	5.401%	$10.8036	$10.80	$10.80	$10.80
Purchase #4	$223.46	12.577%	$251.5646	$251.56	$251.55	$251.60
Purchase #5	$58.73	11.284%	$65.3571	$65.36	$65.35	$65.40
Purchase #6	$82.30	10.465%	$90.9127	$90.91	$90.90	$90.90
Purchase #7	$80.96	6.703%	$86.3867	$86.39	$86.40	$86.40
7 purchase totals =	$938.06		$1,024.1202	$1,024.11	$1,024.10	$1,024.20