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	$96.85	7.567%	$104.1786	$104.18	$104.20	$104.20
Purchase #2	$148.95	10.718%	$164.9145	$164.91	$164.90	$164.90
Purchase #3	$91.33	10.423%	$100.8493	$100.85	$100.85	$100.80
Purchase #4	$215.81	9.228%	$235.7249	$235.72	$235.70	$235.70
Purchase #5	$167.50	6.660%	$178.6555	$178.66	$178.65	$178.70
Purchase #6	$88.30	11.729%	$98.6567	$98.66	$98.65	$98.70
Purchase #7	$243.43	10.123%	$268.0724	$268.07	$268.05	$268.10
7 purchase totals =	$1,052.17		$1,151.0519	$1,151.05	$1,151.00	$1,151.10