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	$109.34	4.370%	$114.1182	$114.12	$114.10	$114.10
Purchase #2	$39.68	8.212%	$42.9385	$42.94	$42.95	$42.90
Purchase #3	$215.83	3.361%	$223.084	$223.08	$223.10	$223.10
Purchase #4	$213.33	10.415%	$235.5483	$235.55	$235.55	$235.50
Purchase #5	$86.28	3.398%	$89.2118	$89.21	$89.20	$89.20
Purchase #6	$131.78	9.676%	$144.531	$144.53	$144.55	$144.50
Purchase #7	$190.62	13.773%	$216.8741	$216.87	$216.85	$216.90
7 purchase totals =	$986.86		$1,066.3059	$1,066.30	$1,066.30	$1,066.20