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	$145.50	4.867%	$152.5815	$152.58	$152.60	$152.60
Purchase #2	$55.82	10.156%	$61.4891	$61.49	$61.50	$61.50
Purchase #3	$199.72	6.175%	$212.0527	$212.05	$212.05	$212.10
Purchase #4	$174.86	3.120%	$180.3156	$180.32	$180.30	$180.30
Purchase #5	$78.28	7.381%	$84.0578	$84.06	$84.05	$84.10
Purchase #6	$236.75	13.649%	$269.064	$269.06	$269.05	$269.10
Purchase #7	$89.87	6.639%	$95.8365	$95.84	$95.85	$95.80
7 purchase totals =	$980.80		$1,055.3972	$1,055.40	$1,055.40	$1,055.50