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	$50.98	4.799%	$53.4265	$53.43	$53.45	$53.40
Purchase #2	$79.59	8.234%	$86.1434	$86.14	$86.15	$86.10
Purchase #3	$52.78	9.277%	$57.6764	$57.68	$57.70	$57.70
Purchase #4	$70.88	3.333%	$73.2424	$73.24	$73.25	$73.20
Purchase #5	$234.32	6.334%	$249.1618	$249.16	$249.15	$249.20
Purchase #6	$87.63	4.357%	$91.448	$91.45	$91.45	$91.40
Purchase #7	$73.45	6.515%	$78.2353	$78.24	$78.25	$78.20
7 purchase totals =	$649.63		$689.3338	$689.34	$689.40	$689.20