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	$140.97	4.391%	$147.16	$147.16	$147.15	$147.20
Purchase #2	$240.51	11.792%	$268.8709	$268.87	$268.85	$268.90
Purchase #3	$132.91	5.564%	$140.3051	$140.31	$140.30	$140.30
Purchase #4	$234.89	4.467%	$245.3825	$245.38	$245.40	$245.40
Purchase #5	$167.50	13.478%	$190.0757	$190.08	$190.10	$190.10
Purchase #6	$158.56	3.468%	$164.0589	$164.06	$164.05	$164.10
Purchase #7	$200.96	6.404%	$213.8295	$213.83	$213.85	$213.80
7 purchase totals =	$1,276.30		$1,369.6826	$1,369.69	$1,369.70	$1,369.80