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	$43.71	3.364%	$45.1804	$45.18	$45.20	$45.20
Purchase #2	$94.33	4.759%	$98.8192	$98.82	$98.80	$98.80
Purchase #3	$209.25	12.109%	$234.5881	$234.59	$234.60	$234.60
Purchase #4	$72.70	4.376%	$75.8814	$75.88	$75.90	$75.90
Purchase #5	$228.28	12.818%	$257.5409	$257.54	$257.55	$257.50
Purchase #6	$118.78	7.833%	$128.084	$128.08	$128.10	$128.10
Purchase #7	$243.78	4.258%	$254.1602	$254.16	$254.15	$254.20
7 purchase totals =	$1,010.83		$1,094.2542	$1,094.25	$1,094.30	$1,094.30