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	$168.95	8.841%	$183.8869	$183.89	$183.90	$183.90
Purchase #2	$37.78	10.128%	$41.6064	$41.61	$41.60	$41.60
Purchase #3	$82.60	8.288%	$89.4459	$89.45	$89.45	$89.40
Purchase #4	$152.53	3.623%	$158.0562	$158.06	$158.05	$158.10
Purchase #5	$96.26	7.410%	$103.3929	$103.39	$103.40	$103.40
Purchase #6	$204.76	6.223%	$217.5022	$217.50	$217.50	$217.50
Purchase #7	$59.28	9.398%	$64.8511	$64.85	$64.85	$64.90
7 purchase totals =	$802.16		$858.7416	$858.75	$858.75	$858.80