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	$140.50	3.122%	$144.8864	$144.89	$144.90	$144.90
Purchase #2	$85.62	8.280%	$92.7093	$92.71	$92.70	$92.70
Purchase #3	$182.46	4.868%	$191.3422	$191.34	$191.35	$191.30
Purchase #4	$185.39	4.278%	$193.321	$193.32	$193.30	$193.30
Purchase #5	$67.37	3.841%	$69.9577	$69.96	$69.95	$70.00
Purchase #6	$156.73	7.752%	$168.8797	$168.88	$168.90	$168.90
Purchase #7	$178.33	8.439%	$193.3793	$193.38	$193.40	$193.40
7 purchase totals =	$996.40		$1,054.4756	$1,054.48	$1,054.50	$1,054.50